Merge pull request #294 from Pylons/py3-only

Remove Python 2 support

40 files changed, 630 insertions, 771 deletions

diff --git a/.github/workflows/ci-tests.yml b/.github/workflows/ci-tests.yml
index 54b229e..c8c660e 100644
--- a/.github/workflows/ci-tests.yml
+++ b/.github/workflows/ci-tests.yml
@@ -15,7 +15,6 @@ jobs:
         strategy:
             matrix:
                 py:
-                    - "2.7"
                     - "3.5"
                     - "3.6"
                     - "3.7"
@@ -56,11 +55,6 @@ jobs:
         name: Validate coverage
         steps:
             - uses: actions/checkout@v2
-            - name: Setup python 2.7
-              uses: actions/setup-python@v2
-              with:
-                  python-version: 2.7
-                  architecture: x64
             - name: Setup python 3.8
               uses: actions/setup-python@v2
               with:
@@ -68,7 +62,7 @@ jobs:
                   architecture: x64
 
             - run: pip install tox
-            - run: tox -e py38,py27,coverage
+            - run: tox -e py38,coverage
     docs:
         runs-on: ubuntu-latest
         name: Build the documentation
diff --git a/CHANGES.txt b/CHANGES.txt
index 5550995..f4d1acc 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -1,3 +1,8 @@
+2.0.0 (unreleased)
+------------------
+
+- Drop Python 2.7 support
+
 1.4.4 (2020-06-01)
 ------------------
 
diff --git a/MANIFEST.in b/MANIFEST.in
index 7540038..b41b4db 100644
--- a/MANIFEST.in
+++ b/MANIFEST.in
@@ -17,5 +17,6 @@ include .coveragerc .flake8
 include tox.ini rtd.txt
 
 exclude TODO.txt
+prune docs/_build
 
 recursive-exclude * __pycache__ *.py[cod]
diff --git a/README.rst b/README.rst
index f9bf1a8..b85e49d 100644
--- a/README.rst
+++ b/README.rst
@@ -16,10 +16,11 @@ Waitress
         :target: https://webchat.freenode.net/?channels=pyramid
         :alt: IRC Freenode
 
-Waitress is meant to be a production-quality pure-Python WSGI server with very
-acceptable performance.  It has no dependencies except ones which live in the
-Python standard library.  It runs on CPython on Unix and Windows under Python
-2.7+ and Python 3.5+.  It is also known to run on PyPy 1.6.0+ on UNIX.  It
-supports HTTP/1.0 and HTTP/1.1.
+Waitress is a production-quality pure-Python WSGI server with very acceptable
+performance. It has no dependencies except ones which live in the Python
+standard library. It runs on CPython on Unix and Windows under Python 3.5+. It
+is also known to run on PyPy (version 3.5 compatible) on UNIX. It supports
+HTTP/1.0 and HTTP/1.1.
 
-For more information, see the "docs" directory of the Waitress package or visit https://docs.pylonsproject.org/projects/waitress/en/latest/
+For more information, see the "docs" directory of the Waitress package or visit
+https://docs.pylonsproject.org/projects/waitress/en/latest/
diff --git a/pyproject.toml b/pyproject.toml
index 7f50ece..b68b905 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -3,10 +3,25 @@ requires = ["setuptools >= 41"]
 build-backend = "setuptools.build_meta"
 
 [tool.black]
-py36 = false
+target-version = ['py35', 'py36', 'py37', 'py38']
 exclude = '''
 /(
   \.git
   | .tox
 )/
 '''
+
+ # This next section only exists for people that have their editors
+# automatically call isort, black already sorts entries on its own when run.
+[tool.isort]
+profile = "black"
+multi_line_output = 3
+src_paths = ["src", "tests"]
+skip_glob = ["docs/*"]
+include_trailing_comma = true
+force_grid_wrap = false
+combine_as_imports = true
+line_length = 88
+force_sort_within_sections = true
+default_section = "THIRDPARTY"
+known_first_party = "waitress"
diff --git a/setup.cfg b/setup.cfg
index a10b6a1..894d563 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -1,6 +1,6 @@
 [metadata]
 name = waitress
-version = 1.4.4
+version = 2.0.0dev0
 description = Waitress WSGI server
 long_description = file: README.rst, CHANGES.txt
 long_description_content_type = text/x-rst
@@ -12,8 +12,6 @@ classifiers =
     Intended Audience :: Developers
     License :: OSI Approved :: Zope Public License
     Programming Language :: Python
-    Programming Language :: Python :: 2
-    Programming Language :: Python :: 2.7
     Programming Language :: Python :: 3
     Programming Language :: Python :: 3.5
     Programming Language :: Python :: 3.6
@@ -39,7 +37,7 @@ maintainer_email = pylons-discuss@googlegroups.com
 package_dir=
     =src
 packages=find:
-python_requires = >=2.7,!=3.0.*,!=3.1.*,!=3.2.*,!=3.3.*,!=3.4.*
+python_requires = >=3.5.0
 
 [options.entry_points]
 paste.server_runner =
@@ -61,13 +59,10 @@ docs =
     docutils
     pylons-sphinx-themes>=1.0.9
 
-[bdist_wheel]
-universal = 1
-
 [tool:pytest]
 python_files = test_*.py
 # For the benefit of test_wasyncore.py
 python_classes = Test_*
 testpaths =
     tests
-addopts = -W always --cov
+addopts = --cov -W always
diff --git a/src/waitress/__init__.py b/src/waitress/__init__.py
index e6e5911..bbb99da 100644
--- a/src/waitress/__init__.py
+++ b/src/waitress/__init__.py
@@ -1,6 +1,7 @@
-from waitress.server import create_server
 import logging
 
+from waitress.server import create_server
+
 
 def serve(app, **kw):
     _server = kw.pop("_server", create_server)  # test shim
diff --git a/src/waitress/adjustments.py b/src/waitress/adjustments.py
index 93439ea..145ac86 100644
--- a/src/waitress/adjustments.py
+++ b/src/waitress/adjustments.py
@@ -17,13 +17,8 @@ import getopt
 import socket
 import warnings
 
+from .compat import HAS_IPV6, WIN
 from .proxy_headers import PROXY_HEADERS
-from .compat import (
-    PY2,
-    WIN,
-    string_types,
-    HAS_IPV6,
-)
 
 truthy = frozenset(("t", "true", "y", "yes", "on", "1"))
 
@@ -52,7 +47,7 @@ def asoctal(s):
 
 
 def aslist_cronly(value):
-    if isinstance(value, string_types):
+    if isinstance(value, str):
         value = filter(None, [x.strip() for x in value.splitlines()])
     return list(value)
 
@@ -100,11 +95,11 @@ class _int_marker(int):
     pass
 
 
-class _bool_marker(object):
+class _bool_marker:
     pass
 
 
-class Adjustments(object):
+class Adjustments:
     """This class contains tunable parameters.
     """
 
@@ -346,7 +341,7 @@ class Adjustments(object):
             else:
                 (host, port) = (i, str(self.port))
 
-            if WIN and PY2:  # pragma: no cover
+            if WIN:  # pragma: no cover
                 try:
                     # Try turning the port into an integer
                     port = int(port)
diff --git a/src/waitress/buffers.py b/src/waitress/buffers.py
index 04f6b42..0086fe8 100644
--- a/src/waitress/buffers.py
+++ b/src/waitress/buffers.py
@@ -22,7 +22,7 @@ COPY_BYTES = 1 << 18  # 256K
 STRBUF_LIMIT = 8192
 
 
-class FileBasedBuffer(object):
+class FileBasedBuffer:
 
     remain = 0
 
@@ -187,7 +187,7 @@ class ReadOnlyFileBasedBuffer(FileBasedBuffer):
         raise NotImplementedError
 
 
-class OverflowableBuffer(object):
+class OverflowableBuffer:
     """
     This buffer implementation has four stages:
     - No data
diff --git a/src/waitress/channel.py b/src/waitress/channel.py
index bc9a2bb..d756b96 100644
--- a/src/waitress/channel.py
+++ b/src/waitress/channel.py
@@ -16,18 +16,9 @@ import threading
 import time
 import traceback
 
-from waitress.buffers import (
-    OverflowableBuffer,
-    ReadOnlyFileBasedBuffer,
-)
-
+from waitress.buffers import OverflowableBuffer, ReadOnlyFileBasedBuffer
 from waitress.parser import HTTPRequestParser
-
-from waitress.task import (
-    ErrorTask,
-    WSGITask,
-)
-
+from waitress.task import ErrorTask, WSGITask
 from waitress.utilities import InternalServerError
 
 from . import wasyncore
@@ -37,7 +28,7 @@ class ClientDisconnected(Exception):
     """ Raised when attempting to write to a closed socket."""
 
 
-class HTTPChannel(wasyncore.dispatcher, object):
+class HTTPChannel(wasyncore.dispatcher):
     """
     Setting self.requests = [somerequest] prevents more requests from being
     received until the out buffers have been flushed.
@@ -85,16 +76,20 @@ class HTTPChannel(wasyncore.dispatcher, object):
         # if there's data in the out buffer or we've been instructed to close
         # the channel (possibly by our server maintenance logic), run
         # handle_write
+
         return self.total_outbufs_len or self.will_close or self.close_when_flushed
 
     def handle_write(self):
         # Precondition: there's data in the out buffer to be sent, or
         # there's a pending will_close request
+
         if not self.connected:
             # we dont want to close the channel twice
+
             return
 
         # try to flush any pending output
+
         if not self.requests:
             # 1. There are no running tasks, so we don't need to try to lock
             #    the outbuf before sending
@@ -116,11 +111,11 @@ class HTTPChannel(wasyncore.dispatcher, object):
         if flush:
             try:
                 flush()
-            except socket.error:
+            except OSError:
                 if self.adj.log_socket_errors:
                     self.logger.exception("Socket error")
                 self.will_close = True
-            except Exception:
+            except Exception:  # pragma: nocover
                 self.logger.exception("Unexpected exception when flushing")
                 self.will_close = True
 
@@ -134,19 +129,29 @@ class HTTPChannel(wasyncore.dispatcher, object):
     def readable(self):
         # We might want to create a new task.  We can only do this if:
         # 1. We're not already about to close the connection.
-        # 2. There's no already currently running task(s).
-        # 3. There's no data in the output buffer that needs to be sent
+        # 2. We're not waiting to flush remaining data before closing the
+        #    connection
+        # 3. There's no already currently running task(s).
+        # 4. There's no data in the output buffer that needs to be sent
         #    before we potentially create a new task.
-        return not (self.will_close or self.requests or self.total_outbufs_len)
+
+        return not (
+            self.will_close
+            or self.close_when_flushed
+            or self.requests
+            or self.total_outbufs_len
+        )
 
     def handle_read(self):
         try:
             data = self.recv(self.adj.recv_bytes)
-        except socket.error:
+        except OSError:
             if self.adj.log_socket_errors:
                 self.logger.exception("Socket error")
             self.handle_close()
+
             return
+
         if data:
             self.last_activity = time.time()
             self.received(data)
@@ -167,9 +172,11 @@ class HTTPChannel(wasyncore.dispatcher, object):
             if request is None:
                 request = self.parser_class(self.adj)
             n = request.received(data)
+
             if request.expect_continue and request.headers_finished:
                 # guaranteed by parser to be a 1.1 request
                 request.expect_continue = False
+
                 if not self.sent_continue:
                     # there's no current task, so we don't need to try to
                     # lock the outbuf to append to it.
@@ -181,14 +188,17 @@ class HTTPChannel(wasyncore.dispatcher, object):
                     self.sent_continue = True
                     self._flush_some()
                     request.completed = False
+
             if request.completed:
                 # The request (with the body) is ready to use.
                 self.request = None
+
                 if not request.empty:
                     requests.append(request)
                 request = None
             else:
                 self.request = request
+
             if n >= len(data):
                 break
             data = data[n:]
@@ -202,6 +212,7 @@ class HTTPChannel(wasyncore.dispatcher, object):
     def _flush_some_if_lockable(self):
         # Since our task may be appending to the outbuf, we try to acquire
         # the lock, but we don't block if we can't.
+
         if self.outbuf_lock.acquire(False):
             try:
                 self._flush_some()
@@ -222,9 +233,11 @@ class HTTPChannel(wasyncore.dispatcher, object):
             # use outbuf.__len__ rather than len(outbuf) FBO of not getting
             # OverflowError on 32-bit Python
             outbuflen = outbuf.__len__()
+
             while outbuflen > 0:
                 chunk = outbuf.get(self.sendbuf_len)
                 num_sent = self.send(chunk)
+
                 if num_sent:
                     outbuf.skip(num_sent, True)
                     outbuflen -= num_sent
@@ -233,9 +246,11 @@ class HTTPChannel(wasyncore.dispatcher, object):
                 else:
                     # failed to write anything, break out entirely
                     dobreak = True
+
                     break
             else:
                 # self.outbufs[-1] must always be a writable outbuf
+
                 if len(self.outbufs) > 1:
                     toclose = self.outbufs.pop(0)
                     try:
@@ -251,6 +266,7 @@ class HTTPChannel(wasyncore.dispatcher, object):
 
         if sent:
             self.last_activity = time.time()
+
             return True
 
         return False
@@ -285,6 +301,7 @@ class HTTPChannel(wasyncore.dispatcher, object):
         fd = self._fileno  # next line sets this to None
         wasyncore.dispatcher.del_channel(self, map)
         ac = self.server.active_channels
+
         if fd in ac:
             del ac[fd]
 
@@ -297,14 +314,17 @@ class HTTPChannel(wasyncore.dispatcher, object):
             # if the socket is closed then interrupt the task so that it
             # can cleanup possibly before the app_iter is exhausted
             raise ClientDisconnected
+
         if data:
             # the async mainloop might be popping data off outbuf; we can
             # block here waiting for it because we're in a task thread
             with self.outbuf_lock:
                 self._flush_outbufs_below_high_watermark()
+
                 if not self.connected:
                     raise ClientDisconnected
                 num_bytes = len(data)
+
                 if data.__class__ is ReadOnlyFileBasedBuffer:
                     # they used wsgi.file_wrapper
                     self.outbufs.append(data)
@@ -321,13 +341,17 @@ class HTTPChannel(wasyncore.dispatcher, object):
                     self.outbufs[-1].append(data)
                     self.current_outbuf_count += num_bytes
                 self.total_outbufs_len += num_bytes
+
                 if self.total_outbufs_len >= self.adj.send_bytes:
                     self.server.pull_trigger()
+
             return num_bytes
+
         return 0
 
     def _flush_outbufs_below_high_watermark(self):
         # check first to avoid locking if possible
+
         if self.total_outbufs_len > self.adj.outbuf_high_watermark:
             with self.outbuf_lock:
                 while (
@@ -342,6 +366,7 @@ class HTTPChannel(wasyncore.dispatcher, object):
         with self.task_lock:
             while self.requests:
                 request = self.requests[0]
+
                 if request.error:
                     task = self.error_task_class(self, request)
                 else:
@@ -357,6 +382,7 @@ class HTTPChannel(wasyncore.dispatcher, object):
                     self.logger.exception(
                         "Exception while serving %s" % task.request.path
                     )
+
                     if not task.wrote_header:
                         if self.adj.expose_tracebacks:
                             body = traceback.format_exc()
@@ -385,8 +411,10 @@ class HTTPChannel(wasyncore.dispatcher, object):
                         task.close_on_finish = True
                 # we cannot allow self.requests to drop to empty til
                 # here; otherwise the mainloop gets confused
+
                 if task.close_on_finish:
                     self.close_when_flushed = True
+
                     for request in self.requests:
                         request.close()
                     self.requests = []
@@ -398,6 +426,7 @@ class HTTPChannel(wasyncore.dispatcher, object):
                     # that we need to account for, otherwise it'd be better
                     # to do this check at the start of the request instead of
                     # at the end to account for consecutive service() calls
+
                     if len(self.requests) > 1:
                         self._flush_outbufs_below_high_watermark()
 
@@ -406,6 +435,7 @@ class HTTPChannel(wasyncore.dispatcher, object):
                     # outbufs across requests which can cause outbufs to
                     # not be deallocated regularly when a connection is open
                     # for a long time
+
                     if self.current_outbuf_count > 0:
                         self.current_outbuf_count = self.adj.outbuf_high_watermark
 
diff --git a/src/waitress/compat.py b/src/waitress/compat.py
index fe72a76..67543b9 100644
--- a/src/waitress/compat.py
+++ b/src/waitress/compat.py
@@ -1,135 +1,15 @@
-import os
-import sys
-import types
 import platform
-import warnings
-
-try:
-    import urlparse
-except ImportError:  # pragma: no cover
-    from urllib import parse as urlparse
-
-try:
-    import fcntl
-except ImportError:  # pragma: no cover
-    fcntl = None  # windows
-
-# True if we are running on Python 3.
-PY2 = sys.version_info[0] == 2
-PY3 = sys.version_info[0] == 3
-
-# True if we are running on Windows
-WIN = platform.system() == "Windows"
-
-if PY3:  # pragma: no cover
-    string_types = (str,)
-    integer_types = (int,)
-    class_types = (type,)
-    text_type = str
-    binary_type = bytes
-    long = int
-else:
-    string_types = (basestring,)
-    integer_types = (int, long)
-    class_types = (type, types.ClassType)
-    text_type = unicode
-    binary_type = str
-    long = long
-
-if PY3:  # pragma: no cover
-    from urllib.parse import unquote_to_bytes
-
-    def unquote_bytes_to_wsgi(bytestring):
-        return unquote_to_bytes(bytestring).decode("latin-1")
-
-
-else:
-    from urlparse import unquote as unquote_to_bytes
-
-    def unquote_bytes_to_wsgi(bytestring):
-        return unquote_to_bytes(bytestring)
-
-
-def text_(s, encoding="latin-1", errors="strict"):
-    """ If ``s`` is an instance of ``binary_type``, return
-    ``s.decode(encoding, errors)``, otherwise return ``s``"""
-    if isinstance(s, binary_type):
-        return s.decode(encoding, errors)
-    return s  # pragma: no cover
-
-
-if PY3:  # pragma: no cover
-
-    def tostr(s):
-        if isinstance(s, text_type):
-            s = s.encode("latin-1")
-        return str(s, "latin-1", "strict")
-
-    def tobytes(s):
-        return bytes(s, "latin-1")
-
-
-else:
-    tostr = str
-
-    def tobytes(s):
-        return s
-
-
-if PY3:  # pragma: no cover
-    import builtins
-
-    exec_ = getattr(builtins, "exec")
-
-    def reraise(tp, value, tb=None):
-        if value is None:
-            value = tp
-        if value.__traceback__ is not tb:
-            raise value.with_traceback(tb)
-        raise value
-
-    del builtins
-
-else:  # pragma: no cover
-
-    def exec_(code, globs=None, locs=None):
-        """Execute code in a namespace."""
-        if globs is None:
-            frame = sys._getframe(1)
-            globs = frame.f_globals
-            if locs is None:
-                locs = frame.f_locals
-            del frame
-        elif locs is None:
-            locs = globs
-        exec("""exec code in globs, locs""")
-
-    exec_(
-        """def reraise(tp, value, tb=None):
-    raise tp, value, tb
-"""
-    )
-
-try:
-    from StringIO import StringIO as NativeIO
-except ImportError:  # pragma: no cover
-    from io import StringIO as NativeIO
-
-try:
-    import httplib
-except ImportError:  # pragma: no cover
-    from http import client as httplib
-
-try:
-    MAXINT = sys.maxint
-except AttributeError:  # pragma: no cover
-    MAXINT = sys.maxsize
-
 
 # Fix for issue reported in https://github.com/Pylons/waitress/issues/138,
 # Python on Windows may not define IPPROTO_IPV6 in socket.
 import socket
+import sys
+import warnings
 
+# True if we are running on Windows
+WIN = platform.system() == "Windows"
+
+MAXINT = sys.maxsize
 HAS_IPV6 = socket.has_ipv6
 
 if hasattr(socket, "IPPROTO_IPV6") and hasattr(socket, "IPV6_V6ONLY"):
@@ -147,33 +27,3 @@ else:  # pragma: no cover
             RuntimeWarning,
         )
         HAS_IPV6 = False
-
-
-def set_nonblocking(fd):  # pragma: no cover
-    if PY3 and sys.version_info[1] >= 5:
-        os.set_blocking(fd, False)
-    elif fcntl is None:
-        raise RuntimeError("no fcntl module present")
-    else:
-        flags = fcntl.fcntl(fd, fcntl.F_GETFL, 0)
-        flags = flags | os.O_NONBLOCK
-        fcntl.fcntl(fd, fcntl.F_SETFL, flags)
-
-
-if PY3:
-    ResourceWarning = ResourceWarning
-else:
-    ResourceWarning = UserWarning
-
-
-def qualname(cls):
-    if PY3:
-        return cls.__qualname__
-    return cls.__name__
-
-
-try:
-    import thread
-except ImportError:
-    # py3
-    import _thread as thread
diff --git a/src/waitress/parser.py b/src/waitress/parser.py
index 765fe59..3b99921 100644
--- a/src/waitress/parser.py
+++ b/src/waitress/parser.py
@@ -16,11 +16,12 @@
 This server uses asyncore to accept connections and do initial
 processing but threads to do work.
 """
-import re
 from io import BytesIO
+import re
+from urllib import parse
+from urllib.parse import unquote_to_bytes
 
 from waitress.buffers import OverflowableBuffer
-from waitress.compat import tostr, unquote_bytes_to_wsgi, urlparse
 from waitress.receiver import ChunkedReceiver, FixedStreamReceiver
 from waitress.utilities import (
     BadRequest,
@@ -29,9 +30,14 @@ from waitress.utilities import (
     ServerNotImplemented,
     find_double_newline,
 )
+
 from .rfc7230 import HEADER_FIELD
 
 
+def unquote_bytes_to_wsgi(bytestring):
+    return unquote_to_bytes(bytestring).decode("latin-1")
+
+
 class ParsingError(Exception):
     pass
 
@@ -40,7 +46,7 @@ class TransferEncodingNotImplemented(Exception):
     pass
 
 
-class HTTPRequestParser(object):
+class HTTPRequestParser:
     """A structure that collects the HTTP request.
 
     Once the stream is completed, the instance is passed to
@@ -79,11 +85,13 @@ class HTTPRequestParser(object):
         bytes consumed.  Sets the completed flag once both the header and the
         body have been received.
         """
+
         if self.completed:
             return 0  # Can't consume any more.
 
         datalen = len(data)
         br = self.body_rcv
+
         if br is None:
             # In header.
             max_header = self.adj.max_request_header_size
@@ -105,12 +113,14 @@ class HTTPRequestParser(object):
             # If the first line + headers is over the max length, we return a
             # RequestHeaderFieldsTooLarge error rather than continuing to
             # attempt to parse the headers.
+
             if self.header_bytes_received >= max_header:
                 self.parse_header(b"GET / HTTP/1.0\r\n")
                 self.error = RequestHeaderFieldsTooLarge(
                     "exceeds max_header of %s" % max_header
                 )
                 self.completed = True
+
                 return consumed
 
             if index >= 0:
@@ -194,6 +204,7 @@ class HTTPRequestParser(object):
         first line of the request).
         """
         index = header_plus.find(b"\r\n")
+
         if index >= 0:
             first_line = header_plus[:index].rstrip()
             header = header_plus[index + 2 :]
@@ -208,6 +219,7 @@ class HTTPRequestParser(object):
         lines = get_header_lines(header)
 
         headers = self.headers
+
         for line in lines:
             header = HEADER_FIELD.match(line)
 
@@ -218,25 +230,26 @@ class HTTPRequestParser(object):
 
             if b"_" in key:
                 # TODO(xistence): Should we drop this request instead?
+
                 continue
 
             # Only strip off whitespace that is considered valid whitespace by
             # RFC7230, don't strip the rest
             value = value.strip(b" \t")
-            key1 = tostr(key.upper().replace(b"-", b"_"))
+            key1 = key.upper().replace(b"-", b"_").decode("latin-1")
             # If a header already exists, we append subsequent values
             # separated by a comma. Applications already need to handle
             # the comma separated values, as HTTP front ends might do
             # the concatenation for you (behavior specified in RFC2616).
             try:
-                headers[key1] += tostr(b", " + value)
+                headers[key1] += (b", " + value).decode("latin-1")
             except KeyError:
-                headers[key1] = tostr(value)
+                headers[key1] = value.decode("latin-1")
 
         # command, uri, version will be bytes
         command, uri, version = crack_first_line(first_line)
-        version = tostr(version)
-        command = tostr(command)
+        version = version.decode("latin-1")
+        command = command.decode("latin-1")
         self.command = command
         self.version = version
         (
@@ -279,6 +292,7 @@ class HTTPRequestParser(object):
                 # Note: the identity transfer-coding was removed in RFC7230:
                 # https://tools.ietf.org/html/rfc7230#appendix-A.2 and is thus
                 # not supported
+
                 if encoding not in {"chunked"}:
                     raise TransferEncodingNotImplemented(
                         "Transfer-Encoding requested is not supported."
@@ -295,6 +309,7 @@ class HTTPRequestParser(object):
 
             expect = headers.get("EXPECT", "").lower()
             self.expect_continue = expect == "100-continue"
+
             if connection.lower() == "close":
                 self.connection_close = True
 
@@ -305,12 +320,14 @@ class HTTPRequestParser(object):
                 raise ParsingError("Content-Length is invalid")
 
             self.content_length = cl
+
             if cl > 0:
                 buf = OverflowableBuffer(self.adj.inbuf_overflow)
                 self.body_rcv = FixedStreamReceiver(cl, buf)
 
     def get_body_stream(self):
         body_rcv = self.body_rcv
+
         if body_rcv is not None:
             return body_rcv.getfile()
         else:
@@ -318,6 +335,7 @@ class HTTPRequestParser(object):
 
     def close(self):
         body_rcv = self.body_rcv
+
         if body_rcv is not None:
             body_rcv.getbuf().close()
 
@@ -345,16 +363,16 @@ def split_uri(uri):
             path, query = path.split(b"?", 1)
     else:
         try:
-            scheme, netloc, path, query, fragment = urlparse.urlsplit(uri)
+            scheme, netloc, path, query, fragment = parse.urlsplit(uri)
         except UnicodeError:
             raise ParsingError("Bad URI")
 
     return (
-        tostr(scheme),
-        tostr(netloc),
+        scheme.decode("latin-1"),
+        netloc.decode("latin-1"),
         unquote_bytes_to_wsgi(path),
-        tostr(query),
-        tostr(fragment),
+        query.decode("latin-1"),
+        fragment.decode("latin-1"),
     )
 
 
@@ -364,20 +382,24 @@ def get_header_lines(header):
     """
     r = []
     lines = header.split(b"\r\n")
+
     for line in lines:
         if not line:
             continue
 
         if b"\r" in line or b"\n" in line:
-            raise ParsingError('Bare CR or LF found in header line "%s"' % tostr(line))
+            raise ParsingError(
+                'Bare CR or LF found in header line "%s"' % str(line, "latin-1")
+            )
 
         if line.startswith((b" ", b"\t")):
             if not r:
                 # https://corte.si/posts/code/pathod/pythonservers/index.html
-                raise ParsingError('Malformed header line "%s"' % tostr(line))
+                raise ParsingError('Malformed header line "%s"' % str(line, "latin-1"))
             r[-1] += line
         else:
             r.append(line)
+
     return r
 
 
@@ -390,6 +412,7 @@ first_line_re = re.compile(
 
 def crack_first_line(line):
     m = first_line_re.match(line)
+
     if m is not None and m.end() == len(line):
         if m.group(3):
             version = m.group(5)
@@ -406,9 +429,11 @@ def crack_first_line(line):
         # unsuspecting souls from sending lowercase HTTP methods to waitress
         # and having the request complete, while servers like nginx drop the
         # request onto the floor.
+
         if method != method.upper():
-            raise ParsingError('Malformed HTTP method "%s"' % tostr(method))
+            raise ParsingError('Malformed HTTP method "%s"' % str(method, "latin-1"))
         uri = m.group(2)
+
         return method, uri, version
     else:
         return b"", b"", b""
diff --git a/src/waitress/proxy_headers.py b/src/waitress/proxy_headers.py
index 1df8b8e..13cb2ed 100644
--- a/src/waitress/proxy_headers.py
+++ b/src/waitress/proxy_headers.py
@@ -1,7 +1,6 @@
 from collections import namedtuple
 
-from .utilities import logger, undquote, BadRequest
-
+from .utilities import BadRequest, logger, undquote
 
 PROXY_HEADERS = frozenset(
     {
@@ -22,7 +21,7 @@ class MalformedProxyHeader(Exception):
         self.header = header
         self.reason = reason
         self.value = value
-        super(MalformedProxyHeader, self).__init__(header, reason, value)
+        super().__init__(header, reason, value)
 
 
 def proxy_headers_middleware(
@@ -53,7 +52,7 @@ def proxy_headers_middleware(
                     ex.reason,
                     ex.value,
                 )
-                error = BadRequest('Header "{0}" malformed.'.format(ex.header))
+                error = BadRequest('Header "{}" malformed.'.format(ex.header))
                 return error.wsgi_response(environ, start_response)
 
         # Clear out the untrusted proxy headers
diff --git a/src/waitress/receiver.py b/src/waitress/receiver.py
index 5d1568d..8785280 100644
--- a/src/waitress/receiver.py
+++ b/src/waitress/receiver.py
@@ -17,7 +17,7 @@
 from waitress.utilities import BadRequest, find_double_newline
 
 
-class FixedStreamReceiver(object):
+class FixedStreamReceiver:
 
     # See IStreamConsumer
     completed = False
@@ -59,7 +59,7 @@ class FixedStreamReceiver(object):
         return self.buf
 
 
-class ChunkedReceiver(object):
+class ChunkedReceiver:
 
     chunk_remainder = 0
     validate_chunk_end = False
diff --git a/src/waitress/rfc7230.py b/src/waitress/rfc7230.py
index cd33c90..9b25fbd 100644
--- a/src/waitress/rfc7230.py
+++ b/src/waitress/rfc7230.py
@@ -5,8 +5,6 @@ needed to properly parse HTTP messages.
 
 import re
 
-from .compat import tobytes
-
 WS = "[ \t]"
 OWS = WS + "{0,}?"
 RWS = WS + "{1,}?"
@@ -46,7 +44,7 @@ FIELD_CONTENT = FIELD_VCHAR + "+(?:[ \t]+" + FIELD_VCHAR + "+)*"
 FIELD_VALUE = "(?:" + FIELD_CONTENT + ")?"
 
 HEADER_FIELD = re.compile(
-    tobytes(
+    (
         "^(?P<name>" + TOKEN + "):" + OWS + "(?P<value>" + FIELD_VALUE + ")" + OWS + "$"
-    )
+    ).encode("latin-1")
 )
diff --git a/src/waitress/runner.py b/src/waitress/runner.py
index 2495084..4fb3e6b 100644
--- a/src/waitress/runner.py
+++ b/src/waitress/runner.py
@@ -14,7 +14,6 @@
 """Command line runner.
 """
 
-from __future__ import print_function, unicode_literals
 
 import getopt
 import os
@@ -191,7 +190,7 @@ RUNNER_PATTERN = re.compile(
 def match(obj_name):
     matches = RUNNER_PATTERN.match(obj_name)
     if not matches:
-        raise ValueError("Malformed application '{0}'".format(obj_name))
+        raise ValueError("Malformed application '{}'".format(obj_name))
     return matches.group("module"), matches.group("object")
 
 
@@ -216,7 +215,7 @@ def resolve(module_name, object_name):
 
 def show_help(stream, name, error=None):  # pragma: no cover
     if error is not None:
-        print("Error: {0}\n".format(error), file=stream)
+        print("Error: {}\n".format(error), file=stream)
     print(HELP.format(name), file=stream)
 
 
@@ -224,7 +223,7 @@ def show_exception(stream):
     exc_type, exc_value = sys.exc_info()[:2]
     args = getattr(exc_value, "args", None)
     print(
-        ("There was an exception ({0}) importing your module.\n").format(
+        ("There was an exception ({}) importing your module.\n").format(
             exc_type.__name__,
         ),
         file=stream,
@@ -232,7 +231,7 @@ def show_exception(stream):
     if args:
         print("It had these arguments: ", file=stream)
         for idx, arg in enumerate(args, start=1):
-            print("{0}. {1}\n".format(idx, arg), file=stream)
+            print("{}. {}\n".format(idx, arg), file=stream)
     else:
         print("It had no arguments.", file=stream)
 
@@ -269,11 +268,11 @@ def run(argv=sys.argv, _serve=serve):
     try:
         app = resolve(module, obj_name)
     except ImportError:
-        show_help(sys.stderr, name, "Bad module '{0}'".format(module))
+        show_help(sys.stderr, name, "Bad module '{}'".format(module))
         show_exception(sys.stderr)
         return 1
     except AttributeError:
-        show_help(sys.stderr, name, "Bad object name '{0}'".format(obj_name))
+        show_help(sys.stderr, name, "Bad object name '{}'".format(obj_name))
         show_exception(sys.stderr)
         return 1
     if kw["call"]:
diff --git a/src/waitress/server.py b/src/waitress/server.py
index ae56699..06bb957 100644
--- a/src/waitress/server.py
+++ b/src/waitress/server.py
@@ -20,13 +20,10 @@ import time
 from waitress import trigger
 from waitress.adjustments import Adjustments
 from waitress.channel import HTTPChannel
+from waitress.compat import IPPROTO_IPV6, IPV6_V6ONLY
 from waitress.task import ThreadedTaskDispatcher
 from waitress.utilities import cleanup_unix_socket
 
-from waitress.compat import (
-    IPPROTO_IPV6,
-    IPV6_V6ONLY,
-)
 from . import wasyncore
 from .proxy_headers import proxy_headers_middleware
 
@@ -137,7 +134,7 @@ def create_server(
 # This class is only ever used if we have multiple listen sockets. It allows
 # the serve() API to call .run() which starts the wasyncore loop, and catches
 # SystemExit/KeyboardInterrupt so that it can atempt to cleanly shut down.
-class MultiSocketServer(object):
+class MultiSocketServer:
     asyncore = wasyncore  # test shim
 
     def __init__(
@@ -172,7 +169,7 @@ class MultiSocketServer(object):
         wasyncore.close_all(self.map)
 
 
-class BaseWSGIServer(wasyncore.dispatcher, object):
+class BaseWSGIServer(wasyncore.dispatcher):
 
     channel_class = HTTPChannel
     next_channel_cleanup = 0
@@ -260,7 +257,7 @@ class BaseWSGIServer(wasyncore.dispatcher, object):
         if server_name == "0.0.0.0" or server_name == "::":
             try:
                 return str(self.socketmod.gethostname())
-            except (socket.error, UnicodeDecodeError):  # pragma: no cover
+            except (OSError, UnicodeDecodeError):  # pragma: no cover
                 # We also deal with UnicodeDecodeError in case of Windows with
                 # non-ascii hostname
                 return "localhost"
@@ -268,7 +265,7 @@ class BaseWSGIServer(wasyncore.dispatcher, object):
         # Now let's try and convert the IP address to a proper hostname
         try:
             server_name = self.socketmod.gethostbyaddr(server_name)[0]
-        except (socket.error, UnicodeDecodeError):  # pragma: no cover
+        except (OSError, UnicodeDecodeError):  # pragma: no cover
             # We also deal with UnicodeDecodeError in case of Windows with
             # non-ascii hostname
             pass
@@ -312,7 +309,7 @@ class BaseWSGIServer(wasyncore.dispatcher, object):
             if v is None:
                 return
             conn, addr = v
-        except socket.error:
+        except OSError:
             # Linux: On rare occasions we get a bogus socket back from
             # accept.  socketmodule.c:makesockaddr complains that the
             # address family is unknown.  We don't want the whole server
@@ -405,7 +402,7 @@ if hasattr(socket, "AF_UNIX"):
             if sockinfo is None:
                 sockinfo = (socket.AF_UNIX, socket.SOCK_STREAM, None, None)
 
-            super(UnixWSGIServer, self).__init__(
+            super().__init__(
                 application,
                 map=map,
                 _start=_start,
@@ -413,7 +410,7 @@ if hasattr(socket, "AF_UNIX"):
                 dispatcher=dispatcher,
                 adj=adj,
                 sockinfo=sockinfo,
-                **kw
+                **kw,
             )
 
         def bind_server_socket(self):
diff --git a/src/waitress/task.py b/src/waitress/task.py
index 6350e34..1bcc540 100644
--- a/src/waitress/task.py
+++ b/src/waitress/task.py
@@ -12,14 +12,13 @@
 #
 ##############################################################################
 
+from collections import deque
 import socket
 import sys
 import threading
 import time
-from collections import deque
 
 from .buffers import ReadOnlyFileBasedBuffer
-from .compat import reraise, tobytes
 from .utilities import build_http_date, logger, queue_logger
 
 rename_headers = {  # or keep them without the HTTP_ prefix added
@@ -41,7 +40,7 @@ hop_by_hop = frozenset(
 )
 
 
-class ThreadedTaskDispatcher(object):
+class ThreadedTaskDispatcher:
     """A Task Dispatcher that creates a thread for each task.
     """
 
@@ -141,7 +140,7 @@ class ThreadedTaskDispatcher(object):
         return False
 
 
-class Task(object):
+class Task:
     close_on_finish = False
     status = "200 OK"
     wrote_header = False
@@ -166,16 +165,13 @@ class Task(object):
 
     def service(self):
         try:
-            try:
-                self.start()
-                self.execute()
-                self.finish()
-            except socket.error:
-                self.close_on_finish = True
-                if self.channel.adj.log_socket_errors:
-                    raise
-        finally:
-            pass
+            self.start()
+            self.execute()
+            self.finish()
+        except OSError:
+            self.close_on_finish = True
+            if self.channel.adj.log_socket_errors:
+                raise
 
     @property
     def has_body(self):
@@ -281,7 +277,7 @@ class Task(object):
         lines = [first_line] + next_lines
         res = "%s\r\n\r\n" % "\r\n".join(lines)
 
-        return tobytes(res)
+        return res.encode("latin-1")
 
     def remove_content_length_header(self):
         response_headers = []
@@ -317,7 +313,7 @@ class Task(object):
             cl = self.content_length
             if self.chunked_response:
                 # use chunked encoding response
-                towrite = tobytes(hex(len(data))[2:].upper()) + b"\r\n"
+                towrite = hex(len(data))[2:].upper().encode("latin-1") + b"\r\n"
                 towrite += data + b"\r\n"
             elif cl is not None:
                 towrite = data[: cl - self.content_bytes_written]
@@ -361,7 +357,7 @@ class ErrorTask(Task):
         self.response_headers.append(("Connection", "close"))
         self.close_on_finish = True
         self.content_length = len(body)
-        self.write(tobytes(body))
+        self.write(body.encode("latin-1"))
 
 
 class WSGITask(Task):
@@ -385,7 +381,7 @@ class WSGITask(Task):
                         # 1. "service" method in task.py
                         # 2. "service" method in channel.py
                         # 3. "handler_thread" method in task.py
-                        reraise(exc_info[0], exc_info[1], exc_info[2])
+                        raise exc_info[1]
                     else:
                         # As per WSGI spec existing headers must be cleared
                         self.response_headers = []
diff --git a/src/waitress/trigger.py b/src/waitress/trigger.py
index 6a57c12..24c4d0d 100644
--- a/src/waitress/trigger.py
+++ b/src/waitress/trigger.py
@@ -12,9 +12,9 @@
 #
 ##############################################################################
 
+import errno
 import os
 import socket
-import errno
 import threading
 
 from . import wasyncore
@@ -50,7 +50,7 @@ from . import wasyncore
 # the main thread is trying to remove some]
 
 
-class _triggerbase(object):
+class _triggerbase:
     """OS-independent base class for OS-dependent trigger class."""
 
     kind = None  # subclass must set to "pipe" or "loopback"; used by repr
@@ -98,7 +98,7 @@ class _triggerbase(object):
     def handle_read(self):
         try:
             self.recv(8192)
-        except (OSError, socket.error):
+        except OSError:
             return
         with self.lock:
             for thunk in self.thunks:
@@ -173,7 +173,7 @@ else:  # pragma: no cover
                 try:
                     w.connect(connect_address)
                     break  # success
-                except socket.error as detail:
+                except OSError as detail:
                     if detail[0] != errno.WSAEADDRINUSE:
                         # "Address already in use" is the only error
                         # I've seen on two WinXP Pro SP2 boxes, under
diff --git a/src/waitress/utilities.py b/src/waitress/utilities.py
index 556bed2..3caaa33 100644
--- a/src/waitress/utilities.py
+++ b/src/waitress/utilities.py
@@ -273,7 +273,7 @@ def cleanup_unix_socket(path):
                 pass
 
 
-class Error(object):
+class Error:
     code = 500
     reason = "Internal Server Error"
 
diff --git a/src/waitress/wasyncore.py b/src/waitress/wasyncore.py
index 09bcafa..9a68c51 100644
--- a/src/waitress/wasyncore.py
+++ b/src/waitress/wasyncore.py
@@ -51,33 +51,31 @@ in the stdlib will be dropped soon.  It is neither a copy of the 2.7 asyncore
 nor the 3.X asyncore; it is a version compatible with either 2.7 or 3.X.
 """
 
-from . import compat
-from . import utilities
-
-import logging
-import select
-import socket
-import sys
-import time
-import warnings
-
-import os
 from errno import (
+    EAGAIN,
     EALREADY,
-    EINPROGRESS,
-    EWOULDBLOCK,
+    EBADF,
+    ECONNABORTED,
     ECONNRESET,
+    EINPROGRESS,
+    EINTR,
     EINVAL,
-    ENOTCONN,
-    ESHUTDOWN,
     EISCONN,
-    EBADF,
-    ECONNABORTED,
+    ENOTCONN,
     EPIPE,
-    EAGAIN,
-    EINTR,
+    ESHUTDOWN,
+    EWOULDBLOCK,
     errorcode,
 )
+import logging
+import os
+import select
+import socket
+import sys
+import time
+import warnings
+
+from . import compat, utilities
 
 _DISCONNECTED = frozenset({ECONNRESET, ENOTCONN, ESHUTDOWN, ECONNABORTED, EPIPE, EBADF})
 
@@ -138,7 +136,7 @@ def readwrite(obj, flags):
             obj.handle_expt_event()
         if flags & (select.POLLHUP | select.POLLERR | select.POLLNVAL):
             obj.handle_close()
-    except socket.error as e:
+    except OSError as e:
         if e.args[0] not in _DISCONNECTED:
             obj.handle_error()
         else:
@@ -172,7 +170,7 @@ def poll(timeout=0.0, map=None):
 
         try:
             r, w, e = select.select(r, w, e, timeout)
-        except select.error as err:
+        except OSError as err:
             if err.args[0] != EINTR:
                 raise
             else:
@@ -218,7 +216,7 @@ def poll2(timeout=0.0, map=None):
 
         try:
             r = pollster.poll(timeout)
-        except select.error as err:
+        except OSError as err:
             if err.args[0] != EINTR:
                 raise
             r = []
@@ -305,7 +303,7 @@ class dispatcher:
             # passed be connected.
             try:
                 self.addr = sock.getpeername()
-            except socket.error as err:
+            except OSError as err:
                 if err.args[0] in (ENOTCONN, EINVAL):
                     # To handle the case where we got an unconnected
                     # socket.
@@ -320,7 +318,7 @@ class dispatcher:
             self.socket = None
 
     def __repr__(self):
-        status = [self.__class__.__module__ + "." + compat.qualname(self.__class__)]
+        status = [self.__class__.__module__ + "." + self.__class__.__qualname__]
         if self.accepting and self.addr:
             status.append("listening")
         elif self.connected:
@@ -368,7 +366,7 @@ class dispatcher:
                 socket.SO_REUSEADDR,
                 self.socket.getsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR) | 1,
             )
-        except socket.error:
+        except OSError:
             pass
 
     # ==================================================
@@ -412,7 +410,7 @@ class dispatcher:
             self.addr = address
             self.handle_connect_event()
         else:
-            raise socket.error(err, errorcode[err])
+            raise OSError(err, errorcode[err])
 
     def accept(self):
         # XXX can return either an address pair or None
@@ -420,7 +418,7 @@ class dispatcher:
             conn, addr = self.socket.accept()
         except TypeError:
             return None
-        except socket.error as why:
+        except OSError as why:
             if why.args[0] in (EWOULDBLOCK, ECONNABORTED, EAGAIN):
                 return None
             else:
@@ -432,7 +430,7 @@ class dispatcher:
         try:
             result = self.socket.send(data)
             return result
-        except socket.error as why:
+        except OSError as why:
             if why.args[0] == EWOULDBLOCK:
                 return 0
             elif why.args[0] in _DISCONNECTED:
@@ -451,7 +449,7 @@ class dispatcher:
                 return b""
             else:
                 return data
-        except socket.error as why:
+        except OSError as why:
             # winsock sometimes raises ENOTCONN
             if why.args[0] in _DISCONNECTED:
                 self.handle_close()
@@ -467,7 +465,7 @@ class dispatcher:
         if self.socket is not None:
             try:
                 self.socket.close()
-            except socket.error as why:
+            except OSError as why:
                 if why.args[0] not in (ENOTCONN, EBADF):
                     raise
 
@@ -501,7 +499,7 @@ class dispatcher:
     def handle_connect_event(self):
         err = self.socket.getsockopt(socket.SOL_SOCKET, socket.SO_ERROR)
         if err != 0:
-            raise socket.error(err, _strerror(err))
+            raise OSError(err, _strerror(err))
         self.handle_connect()
         self.connected = True
         self.connecting = False
@@ -608,7 +606,7 @@ def close_all(map=None, ignore_all=False):
     for x in list(map.values()):  # list() FBO py3
         try:
             x.close()
-        except socket.error as x:
+        except OSError as x:
             if x.args[0] == EBADF:
                 pass
             elif not ignore_all:
@@ -646,7 +644,7 @@ if os.name == "posix":
 
         def __del__(self):
             if self.fd >= 0:
-                warnings.warn("unclosed file %r" % self, compat.ResourceWarning)
+                warnings.warn("unclosed file %r" % self, ResourceWarning)
             self.close()
 
         def recv(self, *args):
@@ -685,7 +683,7 @@ if os.name == "posix":
                 pass
             self.set_file(fd)
             # set it to non-blocking mode
-            compat.set_nonblocking(fd)
+            os.set_blocking(fd, False)
 
         def set_file(self, fd):
             self.socket = file_wrapper(fd)
diff --git a/tests/fixtureapps/filewrapper.py b/tests/fixtureapps/filewrapper.py
index 63df5a6..40b7685 100644
--- a/tests/fixtureapps/filewrapper.py
+++ b/tests/fixtureapps/filewrapper.py
@@ -5,7 +5,7 @@ here = os.path.dirname(os.path.abspath(__file__))
 fn = os.path.join(here, "groundhog1.jpg")
 
 
-class KindaFilelike(object):  # pragma: no cover
+class KindaFilelike:  # pragma: no cover
     def __init__(self, bytes):
         self.bytes = bytes
 
diff --git a/tests/fixtureapps/getline.py b/tests/fixtureapps/getline.py
index 5e0ad3a..bb5b39c 100644
--- a/tests/fixtureapps/getline.py
+++ b/tests/fixtureapps/getline.py
@@ -2,9 +2,9 @@ import sys
 
 if __name__ == "__main__":
     try:
-        from urllib.request import urlopen, URLError
+        from urllib.request import URLError, urlopen
     except ImportError:
-        from urllib2 import urlopen, URLError
+        from urllib2 import URLError, urlopen
 
     url = sys.argv[1]
     headers = {"Content-Type": "text/plain; charset=utf-8"}
diff --git a/tests/fixtureapps/nocl.py b/tests/fixtureapps/nocl.py
index f82bba0..c95a4f5 100644
--- a/tests/fixtureapps/nocl.py
+++ b/tests/fixtureapps/nocl.py
@@ -6,8 +6,7 @@ def chunks(l, n):  # pragma: no cover
 
 
 def gen(body):  # pragma: no cover
-    for chunk in chunks(body, 10):
-        yield chunk
+    yield from chunks(body, 10)
 
 
 def app(environ, start_response):  # pragma: no cover
diff --git a/tests/test_adjustments.py b/tests/test_adjustments.py
index 303c1aa..420ee4c 100644
--- a/tests/test_adjustments.py
+++ b/tests/test_adjustments.py
@@ -1,16 +1,9 @@
-import sys
 import socket
+import sys
+import unittest
 import warnings
 
-from waitress.compat import (
-    PY2,
-    WIN,
-)
-
-if sys.version_info[:2] == (2, 6):  # pragma: no cover
-    import unittest2 as unittest
-else:  # pragma: no cover
-    import unittest
+from waitress.compat import WIN
 
 
 class Test_asbool(unittest.TestCase):
@@ -60,10 +53,12 @@ class Test_as_socket_list(unittest.TestCase):
             socket.socket(socket.AF_INET, socket.SOCK_STREAM),
             socket.socket(socket.AF_INET6, socket.SOCK_STREAM),
         ]
+
         if hasattr(socket, "AF_UNIX"):
             sockets.append(socket.socket(socket.AF_UNIX, socket.SOCK_STREAM))
         new_sockets = as_socket_list(sockets)
         self.assertEqual(sockets, new_sockets)
+
         for sock in sockets:
             sock.close()
 
@@ -77,6 +72,7 @@ class Test_as_socket_list(unittest.TestCase):
         ]
         new_sockets = as_socket_list(sockets)
         self.assertEqual(new_sockets, [sockets[0], sockets[1]])
+
         for sock in [sock for sock in sockets if isinstance(sock, socket.socket)]:
             sock.close()
 
@@ -99,6 +95,7 @@ class TestAdjustments(unittest.TestCase):
             return True
         except socket.gaierror as e:
             # Check to see what the error is
+
             if e.errno == socket.EAI_ADDRFAMILY:
                 return False
             else:
@@ -220,11 +217,12 @@ class TestAdjustments(unittest.TestCase):
         self.assertRaises(ValueError, self._makeOne, listen="127.0.0.1:test")
 
     def test_service_port(self):
-        if WIN and PY2:  # pragma: no cover
-            # On Windows and Python 2 this is broken, so we raise a ValueError
+        if WIN:  # pragma: no cover
+            # On Windows this is broken, so we raise a ValueError
             self.assertRaises(
                 ValueError, self._makeOne, listen="127.0.0.1:http",
             )
+
             return
 
         inst = self._makeOne(listen="127.0.0.1:http 0.0.0.0:https")
@@ -406,6 +404,9 @@ class TestCLI(unittest.TestCase):
 
         return Adjustments.parse_args(argv)
 
+    def assertDictContainsSubset(self, subset, dictionary):
+        self.assertTrue(set(subset.items()) <= set(dictionary.items()))
+
     def test_noargs(self):
         opts, args = self.parse([])
         self.assertDictEqual(opts, {"call": False, "help": False})
diff --git a/tests/test_buffers.py b/tests/test_buffers.py
index a1330ac..01cdc2d 100644
--- a/tests/test_buffers.py
+++ b/tests/test_buffers.py
@@ -1,5 +1,5 @@
-import unittest
 import io
+import unittest
 
 
 class TestFileBasedBuffer(unittest.TestCase):
@@ -413,7 +413,7 @@ class TestOverflowableBuffer(unittest.TestCase):
     def test_prune_with_buf(self):
         inst = self._makeOne()
 
-        class Buf(object):
+        class Buf:
             def prune(self):
                 self.pruned = True
 
@@ -477,7 +477,7 @@ class TestOverflowableBuffer(unittest.TestCase):
         self.buffers_to_close.remove(inst)
 
     def test_close_withbuf(self):
-        class Buffer(object):
+        class Buffer:
             def close(self):
                 self.closed = True
 
@@ -489,7 +489,7 @@ class TestOverflowableBuffer(unittest.TestCase):
         self.buffers_to_close.remove(inst)
 
 
-class KindaFilelike(object):
+class KindaFilelike:
     def __init__(self, bytes, close=None, tellresults=None):
         self.bytes = bytes
         self.tellresults = tellresults
@@ -506,7 +506,7 @@ class Filelike(KindaFilelike):
         return v
 
 
-class DummyBuffer(object):
+class DummyBuffer:
     def __init__(self, length=0):
         self.length = length
 
diff --git a/tests/test_channel.py b/tests/test_channel.py
index 14ef5a0..df3d450 100644
--- a/tests/test_channel.py
+++ b/tests/test_channel.py
@@ -1,5 +1,5 @@
-import unittest
 import io
+import unittest
 
 
 class TestHTTPChannel(unittest.TestCase):
@@ -29,13 +29,13 @@ class TestHTTPChannel(unittest.TestCase):
 
         inst, _, map = self._makeOneWithMap()
 
-        class DummyBuffer(object):
+        class DummyBuffer:
             chunks = []
 
             def append(self, data):
                 self.chunks.append(data)
 
-        class DummyData(object):
+        class DummyData:
             def __len__(self):
                 return MAXINT
 
@@ -195,7 +195,7 @@ class TestHTTPChannel(unittest.TestCase):
         inst.will_close = False
 
         def recv(b):
-            raise socket.error
+            raise OSError
 
         inst.recv = recv
         inst.last_activity = 0
@@ -270,7 +270,7 @@ class TestHTTPChannel(unittest.TestCase):
         class Lock(DummyLock):
             def wait(self):
                 inst.total_outbufs_len = 0
-                super(Lock, self).wait()
+                super().wait()
 
         inst.outbuf_lock = Lock()
         wrote = inst.write_soon(b"xyz")
@@ -367,7 +367,7 @@ class TestHTTPChannel(unittest.TestCase):
 
         inst, sock, map = self._makeOneWithMap()
 
-        class DummyHugeOutbuffer(object):
+        class DummyHugeOutbuffer:
             def __init__(self):
                 self.length = MAXINT + 1
 
@@ -705,7 +705,7 @@ class TestHTTPChannel(unittest.TestCase):
         self.assertEqual(inst.requests, [])
 
 
-class DummySock(object):
+class DummySock:
     blocking = False
     closed = False
 
@@ -732,7 +732,7 @@ class DummySock(object):
         return len(data)
 
 
-class DummyLock(object):
+class DummyLock:
     notified = False
 
     def __init__(self, acquirable=True):
@@ -759,7 +759,7 @@ class DummyLock(object):
         pass
 
 
-class DummyBuffer(object):
+class DummyBuffer:
     closed = False
 
     def __init__(self, data, toraise=None):
@@ -783,7 +783,7 @@ class DummyBuffer(object):
         self.closed = True
 
 
-class DummyAdjustments(object):
+class DummyAdjustments:
     outbuf_overflow = 1048576
     outbuf_high_watermark = 1048576
     inbuf_overflow = 512000
@@ -798,7 +798,7 @@ class DummyAdjustments(object):
     max_request_header_size = 10000
 
 
-class DummyServer(object):
+class DummyServer:
     trigger_pulled = False
     adj = DummyAdjustments()
 
@@ -813,7 +813,7 @@ class DummyServer(object):
         self.trigger_pulled = True
 
 
-class DummyParser(object):
+class DummyParser:
     version = 1
     data = None
     completed = True
@@ -831,7 +831,7 @@ class DummyParser(object):
         return len(data)
 
 
-class DummyRequest(object):
+class DummyRequest:
     error = None
     path = "/"
     version = "1.0"
@@ -844,7 +844,7 @@ class DummyRequest(object):
         self.closed = True
 
 
-class DummyLogger(object):
+class DummyLogger:
     def __init__(self):
         self.exceptions = []
         self.infos = []
@@ -857,13 +857,13 @@ class DummyLogger(object):
         self.exceptions.append(msg)
 
 
-class DummyError(object):
+class DummyError:
     code = "431"
     reason = "Bleh"
     body = "My body"
 
 
-class DummyTaskClass(object):
+class DummyTaskClass:
     wrote_header = True
     close_on_finish = False
     serviced = False
diff --git a/tests/test_compat.py b/tests/test_compat.py
deleted file mode 100644
index 37c2193..0000000
--- a/tests/test_compat.py
+++ /dev/null
@@ -1,22 +0,0 @@
-# -*- coding: utf-8 -*-
-
-import unittest
-
-
-class Test_unquote_bytes_to_wsgi(unittest.TestCase):
-    def _callFUT(self, v):
-        from waitress.compat import unquote_bytes_to_wsgi
-
-        return unquote_bytes_to_wsgi(v)
-
-    def test_highorder(self):
-        from waitress.compat import PY3
-
-        val = b"/a%C5%9B"
-        result = self._callFUT(val)
-        if PY3:  # pragma: no cover
-            # PEP 3333 urlunquoted-latin1-decoded-bytes
-            self.assertEqual(result, "/aÅ\x9b")
-        else:  # pragma: no cover
-            # sanity
-            self.assertEqual(result, b"/a\xc5\x9b")
diff --git a/tests/test_functional.py b/tests/test_functional.py
index e894497..c99876d 100644
--- a/tests/test_functional.py
+++ b/tests/test_functional.py
@@ -1,4 +1,5 @@
 import errno
+from http import client as httplib
 import logging
 import multiprocessing
 import os
@@ -9,8 +10,8 @@ import subprocess
 import sys
 import time
 import unittest
+
 from waitress import server
-from waitress.compat import httplib, tobytes
 from waitress.utilities import cleanup_unix_socket
 
 dn = os.path.dirname
@@ -54,14 +55,15 @@ class FixtureTcpWSGIServer(server.TcpWSGIServer):
     def __init__(self, application, queue, **kw):  # pragma: no cover
         # Coverage doesn't see this as it's ran in a separate process.
         kw["port"] = 0  # Bind to any available port.
-        super(FixtureTcpWSGIServer, self).__init__(application, **kw)
+        super().__init__(application, **kw)
         host, port = self.socket.getsockname()
+
         if os.name == "nt":
             host = "127.0.0.1"
         queue.put((host, port))
 
 
-class SubprocessTests(object):
+class SubprocessTests:
 
     # For nose: all tests may be ran in separate processes.
     _multiprocess_can_split_ = True
@@ -98,9 +100,9 @@ class SubprocessTests(object):
 
     def assertline(self, line, status, reason, version):
         v, s, r = (x.strip() for x in line.split(None, 2))
-        self.assertEqual(s, tobytes(status))
-        self.assertEqual(r, tobytes(reason))
-        self.assertEqual(v, tobytes(version))
+        self.assertEqual(s, status.encode("latin-1"))
+        self.assertEqual(r, reason.encode("latin-1"))
+        self.assertEqual(v, version.encode("latin-1"))
 
     def create_socket(self):
         return socket.socket(self.server.family, socket.SOCK_STREAM)
@@ -142,9 +144,11 @@ class SleepyThreadTests(TcpTests, unittest.TestCase):
         )
         r, w = os.pipe()
         procs = []
+
         for cmd in cmds:
             procs.append(subprocess.Popen(cmd, stdout=w))
         time.sleep(3)
+
         for proc in procs:
             if proc.returncode is not None:  # pragma: no cover
                 proc.terminate()
@@ -158,7 +162,7 @@ class SleepyThreadTests(TcpTests, unittest.TestCase):
         self.assertEqual(result, b"notsleepy returnedsleepy returned")
 
 
-class EchoTests(object):
+class EchoTests:
     def setUp(self):
         from tests.fixtureapps import echo
 
@@ -177,11 +181,11 @@ class EchoTests(object):
         from tests.fixtureapps import echo
 
         line, headers, body = read_http(fp)
+
         return line, headers, echo.parse_response(body)
 
     def test_date_and_server(self):
-        to_send = "GET / HTTP/1.0\r\nContent-Length: 0\r\n\r\n"
-        to_send = tobytes(to_send)
+        to_send = b"GET / HTTP/1.0\r\nContent-Length: 0\r\n\r\n"
         self.connect()
         self.sock.send(to_send)
         fp = self.sock.makefile("rb", 0)
@@ -192,8 +196,7 @@ class EchoTests(object):
 
     def test_bad_host_header(self):
         # https://corte.si/posts/code/pathod/pythonservers/index.html
-        to_send = "GET / HTTP/1.0\r\n Host: 0\r\n\r\n"
-        to_send = tobytes(to_send)
+        to_send = b"GET / HTTP/1.0\r\n Host: 0\r\n\r\n"
         self.connect()
         self.sock.send(to_send)
         fp = self.sock.makefile("rb", 0)
@@ -203,9 +206,8 @@ class EchoTests(object):
         self.assertTrue(headers.get("date"))
 
     def test_send_with_body(self):
-        to_send = "GET / HTTP/1.0\r\nContent-Length: 5\r\n\r\n"
-        to_send += "hello"
-        to_send = tobytes(to_send)
+        to_send = b"GET / HTTP/1.0\r\nContent-Length: 5\r\n\r\n"
+        to_send += b"hello"
         self.connect()
         self.sock.send(to_send)
         fp = self.sock.makefile("rb", 0)
@@ -215,8 +217,7 @@ class EchoTests(object):
         self.assertEqual(echo.body, b"hello")
 
     def test_send_empty_body(self):
-        to_send = "GET / HTTP/1.0\r\nContent-Length: 0\r\n\r\n"
-        to_send = tobytes(to_send)
+        to_send = b"GET / HTTP/1.0\r\nContent-Length: 0\r\n\r\n"
         self.connect()
         self.sock.send(to_send)
         fp = self.sock.makefile("rb", 0)
@@ -227,6 +228,7 @@ class EchoTests(object):
 
     def test_multiple_requests_with_body(self):
         orig_sock = self.sock
+
         for x in range(3):
             self.sock = self.create_socket()
             self.test_send_with_body()
@@ -235,6 +237,7 @@ class EchoTests(object):
 
     def test_multiple_requests_without_body(self):
         orig_sock = self.sock
+
         for x in range(3):
             self.sock = self.create_socket()
             self.test_send_empty_body()
@@ -242,13 +245,13 @@ class EchoTests(object):
         self.sock = orig_sock
 
     def test_without_crlf(self):
-        data = "Echo\r\nthis\r\nplease"
-        s = tobytes(
-            "GET / HTTP/1.0\r\n"
-            "Connection: close\r\n"
-            "Content-Length: %d\r\n"
-            "\r\n"
-            "%s" % (len(data), data)
+        data = b"Echo\r\nthis\r\nplease"
+        s = (
+            b"GET / HTTP/1.0\r\n"
+            b"Connection: close\r\n"
+            b"Content-Length: %d\r\n"
+            b"\r\n"
+            b"%s" % (len(data), data)
         )
         self.connect()
         self.sock.send(s)
@@ -257,40 +260,42 @@ class EchoTests(object):
         self.assertline(line, "200", "OK", "HTTP/1.0")
         self.assertEqual(int(echo.content_length), len(data))
         self.assertEqual(len(echo.body), len(data))
-        self.assertEqual(echo.body, tobytes(data))
+        self.assertEqual(echo.body, (data))
 
     def test_large_body(self):
         # 1024 characters.
-        body = "This string has 32 characters.\r\n" * 32
-        s = tobytes(
-            "GET / HTTP/1.0\r\nContent-Length: %d\r\n\r\n%s" % (len(body), body)
-        )
+        body = b"This string has 32 characters.\r\n" * 32
+        s = b"GET / HTTP/1.0\r\nContent-Length: %d\r\n\r\n%s" % (len(body), body)
         self.connect()
         self.sock.send(s)
         fp = self.sock.makefile("rb", 0)
         line, headers, echo = self._read_echo(fp)
         self.assertline(line, "200", "OK", "HTTP/1.0")
         self.assertEqual(echo.content_length, "1024")
-        self.assertEqual(echo.body, tobytes(body))
+        self.assertEqual(echo.body, body)
 
     def test_many_clients(self):
         conns = []
+
         for n in range(50):
             h = self.make_http_connection()
             h.request("GET", "/", headers={"Accept": "text/plain"})
             conns.append(h)
         responses = []
+
         for h in conns:
             response = h.getresponse()
             self.assertEqual(response.status, 200)
             responses.append(response)
+
         for response in responses:
             response.read()
+
         for h in conns:
             h.close()
 
     def test_chunking_request_without_content(self):
-        header = tobytes("GET / HTTP/1.1\r\nTransfer-Encoding: chunked\r\n\r\n")
+        header = b"GET / HTTP/1.1\r\nTransfer-Encoding: chunked\r\n\r\n"
         self.connect()
         self.sock.send(header)
         self.sock.send(b"0\r\n\r\n")
@@ -305,10 +310,11 @@ class EchoTests(object):
         control_line = b"20;\r\n"  # 20 hex = 32 dec
         s = b"This string has 32 characters.\r\n"
         expected = s * 12
-        header = tobytes("GET / HTTP/1.1\r\nTransfer-Encoding: chunked\r\n\r\n")
+        header = b"GET / HTTP/1.1\r\nTransfer-Encoding: chunked\r\n\r\n"
         self.connect()
         self.sock.send(header)
         fp = self.sock.makefile("rb", 0)
+
         for n in range(12):
             self.sock.send(control_line)
             self.sock.send(s)
@@ -321,13 +327,12 @@ class EchoTests(object):
         self.assertFalse("transfer-encoding" in headers)
 
     def test_broken_chunked_encoding(self):
-        control_line = "20;\r\n"  # 20 hex = 32 dec
-        s = "This string has 32 characters.\r\n"
-        to_send = "GET / HTTP/1.1\r\nTransfer-Encoding: chunked\r\n\r\n"
-        to_send += control_line + s + "\r\n"
+        control_line = b"20;\r\n"  # 20 hex = 32 dec
+        s = b"This string has 32 characters.\r\n"
+        to_send = b"GET / HTTP/1.1\r\nTransfer-Encoding: chunked\r\n\r\n"
+        to_send += control_line + s + b"\r\n"
         # garbage in input
-        to_send += "garbage\r\n"
-        to_send = tobytes(to_send)
+        to_send += b"garbage\r\n"
         self.connect()
         self.sock.send(to_send)
         fp = self.sock.makefile("rb", 0)
@@ -346,13 +351,12 @@ class EchoTests(object):
         self.assertRaises(ConnectionClosed, read_http, fp)
 
     def test_broken_chunked_encoding_missing_chunk_end(self):
-        control_line = "20;\r\n"  # 20 hex = 32 dec
-        s = "This string has 32 characters.\r\n"
-        to_send = "GET / HTTP/1.1\r\nTransfer-Encoding: chunked\r\n\r\n"
+        control_line = b"20;\r\n"  # 20 hex = 32 dec
+        s = b"This string has 32 characters.\r\n"
+        to_send = b"GET / HTTP/1.1\r\nTransfer-Encoding: chunked\r\n\r\n"
         to_send += control_line + s
         # garbage in input
-        to_send += "garbage"
-        to_send = tobytes(to_send)
+        to_send += b"garbage"
         self.connect()
         self.sock.send(to_send)
         fp = self.sock.makefile("rb", 0)
@@ -373,10 +377,8 @@ class EchoTests(object):
 
     def test_keepalive_http_10(self):
         # Handling of Keep-Alive within HTTP 1.0
-        data = "Default: Don't keep me alive"
-        s = tobytes(
-            "GET / HTTP/1.0\r\nContent-Length: %d\r\n\r\n%s" % (len(data), data)
-        )
+        data = b"Default: Don't keep me alive"
+        s = b"GET / HTTP/1.0\r\nContent-Length: %d\r\n\r\n%s" % (len(data), data)
         self.connect()
         self.sock.send(s)
         response = httplib.HTTPResponse(self.sock)
@@ -391,13 +393,13 @@ class EchoTests(object):
         # If header Connection: Keep-Alive is explicitly sent,
         # we want to keept the connection open, we also need to return
         # the corresponding header
-        data = "Keep me alive"
-        s = tobytes(
-            "GET / HTTP/1.0\r\n"
-            "Connection: Keep-Alive\r\n"
-            "Content-Length: %d\r\n"
-            "\r\n"
-            "%s" % (len(data), data)
+        data = b"Keep me alive"
+        s = (
+            b"GET / HTTP/1.0\r\n"
+            b"Connection: Keep-Alive\r\n"
+            b"Content-Length: %d\r\n"
+            b"\r\n"
+            b"%s" % (len(data), data)
         )
         self.connect()
         self.sock.send(s)
@@ -411,10 +413,8 @@ class EchoTests(object):
         # Handling of Keep-Alive within HTTP 1.1
 
         # All connections are kept alive, unless stated otherwise
-        data = "Default: Keep me alive"
-        s = tobytes(
-            "GET / HTTP/1.1\r\nContent-Length: %d\r\n\r\n%s" % (len(data), data)
-        )
+        data = b"Default: Keep me alive"
+        s = b"GET / HTTP/1.1\r\nContent-Length: %d\r\n\r\n%s" % (len(data), data)
         self.connect()
         self.sock.send(s)
         response = httplib.HTTPResponse(self.sock)
@@ -424,13 +424,13 @@ class EchoTests(object):
 
     def test_keepalive_http11_explicit(self):
         # Explicitly set keep-alive
-        data = "Default: Keep me alive"
-        s = tobytes(
-            "GET / HTTP/1.1\r\n"
-            "Connection: keep-alive\r\n"
-            "Content-Length: %d\r\n"
-            "\r\n"
-            "%s" % (len(data), data)
+        data = b"Default: Keep me alive"
+        s = (
+            b"GET / HTTP/1.1\r\n"
+            b"Connection: keep-alive\r\n"
+            b"Content-Length: %d\r\n"
+            b"\r\n"
+            b"%s" % (len(data), data)
         )
         self.connect()
         self.sock.send(s)
@@ -441,13 +441,13 @@ class EchoTests(object):
 
     def test_keepalive_http11_connclose(self):
         # specifying Connection: close explicitly
-        data = "Don't keep me alive"
-        s = tobytes(
-            "GET / HTTP/1.1\r\n"
-            "Connection: close\r\n"
-            "Content-Length: %d\r\n"
-            "\r\n"
-            "%s" % (len(data), data)
+        data = b"Don't keep me alive"
+        s = (
+            b"GET / HTTP/1.1\r\n"
+            b"Connection: close\r\n"
+            b"Content-Length: %d\r\n"
+            b"\r\n"
+            b"%s" % (len(data), data)
         )
         self.connect()
         self.sock.send(s)
@@ -458,14 +458,13 @@ class EchoTests(object):
 
     def test_proxy_headers(self):
         to_send = (
-            "GET / HTTP/1.0\r\n"
-            "Content-Length: 0\r\n"
-            "Host: www.google.com:8080\r\n"
-            "X-Forwarded-For: 192.168.1.1\r\n"
-            "X-Forwarded-Proto: https\r\n"
-            "X-Forwarded-Port: 5000\r\n\r\n"
+            b"GET / HTTP/1.0\r\n"
+            b"Content-Length: 0\r\n"
+            b"Host: www.google.com:8080\r\n"
+            b"X-Forwarded-For: 192.168.1.1\r\n"
+            b"X-Forwarded-Proto: https\r\n"
+            b"X-Forwarded-Port: 5000\r\n\r\n"
         )
-        to_send = tobytes(to_send)
         self.connect()
         self.sock.send(to_send)
         fp = self.sock.makefile("rb", 0)
@@ -480,7 +479,7 @@ class EchoTests(object):
         self.assertEqual(echo.remote_host, "192.168.1.1")
 
 
-class PipeliningTests(object):
+class PipeliningTests:
     def setUp(self):
         from tests.fixtureapps import echo
 
@@ -491,27 +490,30 @@ class PipeliningTests(object):
 
     def test_pipelining(self):
         s = (
-            "GET / HTTP/1.0\r\n"
-            "Connection: %s\r\n"
-            "Content-Length: %d\r\n"
-            "\r\n"
-            "%s"
+            b"GET / HTTP/1.0\r\n"
+            b"Connection: %s\r\n"
+            b"Content-Length: %d\r\n"
+            b"\r\n"
+            b"%s"
         )
         to_send = b""
         count = 25
+
         for n in range(count):
-            body = "Response #%d\r\n" % (n + 1)
+            body = b"Response #%d\r\n" % (n + 1)
+
             if n + 1 < count:
-                conn = "keep-alive"
+                conn = b"keep-alive"
             else:
-                conn = "close"
-            to_send += tobytes(s % (conn, len(body), body))
+                conn = b"close"
+            to_send += s % (conn, len(body), body)
 
         self.connect()
         self.sock.send(to_send)
         fp = self.sock.makefile("rb", 0)
+
         for n in range(count):
-            expect_body = tobytes("Response #%d\r\n" % (n + 1))
+            expect_body = b"Response #%d\r\n" % (n + 1)
             line = fp.readline()  # status line
             version, status, reason = (x.strip() for x in line.split(None, 2))
             headers = parse_headers(fp)
@@ -522,7 +524,7 @@ class PipeliningTests(object):
             self.assertEqual(response_body, expect_body)
 
 
-class ExpectContinueTests(object):
+class ExpectContinueTests:
     def setUp(self):
         from tests.fixtureapps import echo
 
@@ -533,14 +535,14 @@ class ExpectContinueTests(object):
 
     def test_expect_continue(self):
         # specifying Connection: close explicitly
-        data = "I have expectations"
-        to_send = tobytes(
-            "GET / HTTP/1.1\r\n"
-            "Connection: close\r\n"
-            "Content-Length: %d\r\n"
-            "Expect: 100-continue\r\n"
-            "\r\n"
-            "%s" % (len(data), data)
+        data = b"I have expectations"
+        to_send = (
+            b"GET / HTTP/1.1\r\n"
+            b"Connection: close\r\n"
+            b"Content-Length: %d\r\n"
+            b"Expect: 100-continue\r\n"
+            b"\r\n"
+            b"%s" % (len(data), data)
         )
         self.connect()
         self.sock.send(to_send)
@@ -558,10 +560,10 @@ class ExpectContinueTests(object):
         response_body = fp.read(length)
         self.assertEqual(int(status), 200)
         self.assertEqual(length, len(response_body))
-        self.assertEqual(response_body, tobytes(data))
+        self.assertEqual(response_body, data)
 
 
-class BadContentLengthTests(object):
+class BadContentLengthTests:
     def setUp(self):
         from tests.fixtureapps import badcl
 
@@ -573,11 +575,11 @@ class BadContentLengthTests(object):
     def test_short_body(self):
         # check to see if server closes connection when body is too short
         # for cl header
-        to_send = tobytes(
-            "GET /short_body HTTP/1.0\r\n"
-            "Connection: Keep-Alive\r\n"
-            "Content-Length: 0\r\n"
-            "\r\n"
+        to_send = (
+            b"GET /short_body HTTP/1.0\r\n"
+            b"Connection: Keep-Alive\r\n"
+            b"Content-Length: 0\r\n"
+            b"\r\n"
         )
         self.connect()
         self.sock.send(to_send)
@@ -590,7 +592,7 @@ class BadContentLengthTests(object):
         self.assertEqual(int(status), 200)
         self.assertNotEqual(content_length, len(response_body))
         self.assertEqual(len(response_body), content_length - 1)
-        self.assertEqual(response_body, tobytes("abcdefghi"))
+        self.assertEqual(response_body, b"abcdefghi")
         # remote closed connection (despite keepalive header); not sure why
         # first send succeeds
         self.send_check_error(to_send)
@@ -599,11 +601,11 @@ class BadContentLengthTests(object):
     def test_long_body(self):
         # check server doesnt close connection when body is too short
         # for cl header
-        to_send = tobytes(
-            "GET /long_body HTTP/1.0\r\n"
-            "Connection: Keep-Alive\r\n"
-            "Content-Length: 0\r\n"
-            "\r\n"
+        to_send = (
+            b"GET /long_body HTTP/1.0\r\n"
+            b"Connection: Keep-Alive\r\n"
+            b"Content-Length: 0\r\n"
+            b"\r\n"
         )
         self.connect()
         self.sock.send(to_send)
@@ -615,7 +617,7 @@ class BadContentLengthTests(object):
         response_body = fp.read(content_length)
         self.assertEqual(int(status), 200)
         self.assertEqual(content_length, len(response_body))
-        self.assertEqual(response_body, tobytes("abcdefgh"))
+        self.assertEqual(response_body, b"abcdefgh")
         # remote does not close connection (keepalive header)
         self.sock.send(to_send)
         fp = self.sock.makefile("rb", 0)
@@ -627,7 +629,7 @@ class BadContentLengthTests(object):
         self.assertEqual(int(status), 200)
 
 
-class NoContentLengthTests(object):
+class NoContentLengthTests:
     def setUp(self):
         from tests.fixtureapps import nocl
 
@@ -637,14 +639,13 @@ class NoContentLengthTests(object):
         self.stop_subprocess()
 
     def test_http10_generator(self):
-        body = string.ascii_letters
+        body = string.ascii_letters.encode("latin-1")
         to_send = (
-            "GET / HTTP/1.0\r\n"
-            "Connection: Keep-Alive\r\n"
-            "Content-Length: %d\r\n\r\n" % len(body)
+            b"GET / HTTP/1.0\r\n"
+            b"Connection: Keep-Alive\r\n"
+            b"Content-Length: %d\r\n\r\n" % len(body)
         )
         to_send += body
-        to_send = tobytes(to_send)
         self.connect()
         self.sock.send(to_send)
         fp = self.sock.makefile("rb", 0)
@@ -652,21 +653,20 @@ class NoContentLengthTests(object):
         self.assertline(line, "200", "OK", "HTTP/1.0")
         self.assertEqual(headers.get("content-length"), None)
         self.assertEqual(headers.get("connection"), "close")
-        self.assertEqual(response_body, tobytes(body))
+        self.assertEqual(response_body, body)
         # remote closed connection (despite keepalive header), because
         # generators cannot have a content-length divined
         self.send_check_error(to_send)
         self.assertRaises(ConnectionClosed, read_http, fp)
 
     def test_http10_list(self):
-        body = string.ascii_letters
+        body = string.ascii_letters.encode("latin-1")
         to_send = (
-            "GET /list HTTP/1.0\r\n"
-            "Connection: Keep-Alive\r\n"
-            "Content-Length: %d\r\n\r\n" % len(body)
+            b"GET /list HTTP/1.0\r\n"
+            b"Connection: Keep-Alive\r\n"
+            b"Content-Length: %d\r\n\r\n" % len(body)
         )
         to_send += body
-        to_send = tobytes(to_send)
         self.connect()
         self.sock.send(to_send)
         fp = self.sock.makefile("rb", 0)
@@ -674,7 +674,7 @@ class NoContentLengthTests(object):
         self.assertline(line, "200", "OK", "HTTP/1.0")
         self.assertEqual(headers["content-length"], str(len(body)))
         self.assertEqual(headers.get("connection"), "Keep-Alive")
-        self.assertEqual(response_body, tobytes(body))
+        self.assertEqual(response_body, body)
         # remote keeps connection open because it divined the content length
         # from a length-1 list
         self.sock.send(to_send)
@@ -682,14 +682,13 @@ class NoContentLengthTests(object):
         self.assertline(line, "200", "OK", "HTTP/1.0")
 
     def test_http10_listlentwo(self):
-        body = string.ascii_letters
+        body = string.ascii_letters.encode("latin-1")
         to_send = (
-            "GET /list_lentwo HTTP/1.0\r\n"
-            "Connection: Keep-Alive\r\n"
-            "Content-Length: %d\r\n\r\n" % len(body)
+            b"GET /list_lentwo HTTP/1.0\r\n"
+            b"Connection: Keep-Alive\r\n"
+            b"Content-Length: %d\r\n\r\n" % len(body)
         )
         to_send += body
-        to_send = tobytes(to_send)
         self.connect()
         self.sock.send(to_send)
         fp = self.sock.makefile("rb", 0)
@@ -697,7 +696,7 @@ class NoContentLengthTests(object):
         self.assertline(line, "200", "OK", "HTTP/1.0")
         self.assertEqual(headers.get("content-length"), None)
         self.assertEqual(headers.get("connection"), "close")
-        self.assertEqual(response_body, tobytes(body))
+        self.assertEqual(response_body, body)
         # remote closed connection (despite keepalive header), because
         # lists of length > 1 cannot have their content length divined
         self.send_check_error(to_send)
@@ -705,18 +704,20 @@ class NoContentLengthTests(object):
 
     def test_http11_generator(self):
         body = string.ascii_letters
-        to_send = "GET / HTTP/1.1\r\nContent-Length: %s\r\n\r\n" % len(body)
+        body = body.encode("latin-1")
+        to_send = b"GET / HTTP/1.1\r\nContent-Length: %d\r\n\r\n" % len(body)
         to_send += body
-        to_send = tobytes(to_send)
         self.connect()
         self.sock.send(to_send)
         fp = self.sock.makefile("rb")
         line, headers, response_body = read_http(fp)
         self.assertline(line, "200", "OK", "HTTP/1.1")
         expected = b""
+
         for chunk in chunks(body, 10):
-            expected += tobytes(
-                "%s\r\n%s\r\n" % (str(hex(len(chunk))[2:].upper()), chunk)
+            expected += b"%s\r\n%s\r\n" % (
+                hex(len(chunk))[2:].upper().encode("latin-1"),
+                chunk,
             )
         expected += b"0\r\n\r\n"
         self.assertEqual(response_body, expected)
@@ -725,17 +726,16 @@ class NoContentLengthTests(object):
         self.assertRaises(ConnectionClosed, read_http, fp)
 
     def test_http11_list(self):
-        body = string.ascii_letters
-        to_send = "GET /list HTTP/1.1\r\nContent-Length: %d\r\n\r\n" % len(body)
+        body = string.ascii_letters.encode("latin-1")
+        to_send = b"GET /list HTTP/1.1\r\nContent-Length: %d\r\n\r\n" % len(body)
         to_send += body
-        to_send = tobytes(to_send)
         self.connect()
         self.sock.send(to_send)
         fp = self.sock.makefile("rb", 0)
         line, headers, response_body = read_http(fp)
         self.assertline(line, "200", "OK", "HTTP/1.1")
         self.assertEqual(headers["content-length"], str(len(body)))
-        self.assertEqual(response_body, tobytes(body))
+        self.assertEqual(response_body, body)
         # remote keeps connection open because it divined the content length
         # from a length-1 list
         self.sock.send(to_send)
@@ -743,19 +743,20 @@ class NoContentLengthTests(object):
         self.assertline(line, "200", "OK", "HTTP/1.1")
 
     def test_http11_listlentwo(self):
-        body = string.ascii_letters
-        to_send = "GET /list_lentwo HTTP/1.1\r\nContent-Length: %s\r\n\r\n" % len(body)
+        body = string.ascii_letters.encode("latin-1")
+        to_send = b"GET /list_lentwo HTTP/1.1\r\nContent-Length: %d\r\n\r\n" % len(body)
         to_send += body
-        to_send = tobytes(to_send)
         self.connect()
         self.sock.send(to_send)
         fp = self.sock.makefile("rb")
         line, headers, response_body = read_http(fp)
         self.assertline(line, "200", "OK", "HTTP/1.1")
         expected = b""
-        for chunk in (body[0], body[1:]):
-            expected += tobytes(
-                "%s\r\n%s\r\n" % (str(hex(len(chunk))[2:].upper()), chunk)
+
+        for chunk in (body[:1], body[1:]):
+            expected += b"%s\r\n%s\r\n" % (
+                (hex(len(chunk))[2:].upper().encode("latin-1")),
+                chunk,
             )
         expected += b"0\r\n\r\n"
         self.assertEqual(response_body, expected)
@@ -764,7 +765,7 @@ class NoContentLengthTests(object):
         self.assertRaises(ConnectionClosed, read_http, fp)
 
 
-class WriteCallbackTests(object):
+class WriteCallbackTests:
     def setUp(self):
         from tests.fixtureapps import writecb
 
@@ -776,11 +777,11 @@ class WriteCallbackTests(object):
     def test_short_body(self):
         # check to see if server closes connection when body is too short
         # for cl header
-        to_send = tobytes(
-            "GET /short_body HTTP/1.0\r\n"
-            "Connection: Keep-Alive\r\n"
-            "Content-Length: 0\r\n"
-            "\r\n"
+        to_send = (
+            b"GET /short_body HTTP/1.0\r\n"
+            b"Connection: Keep-Alive\r\n"
+            b"Content-Length: 0\r\n"
+            b"\r\n"
         )
         self.connect()
         self.sock.send(to_send)
@@ -792,7 +793,7 @@ class WriteCallbackTests(object):
         self.assertEqual(cl, 9)
         self.assertNotEqual(cl, len(response_body))
         self.assertEqual(len(response_body), cl - 1)
-        self.assertEqual(response_body, tobytes("abcdefgh"))
+        self.assertEqual(response_body, b"abcdefgh")
         # remote closed connection (despite keepalive header)
         self.send_check_error(to_send)
         self.assertRaises(ConnectionClosed, read_http, fp)
@@ -800,11 +801,11 @@ class WriteCallbackTests(object):
     def test_long_body(self):
         # check server doesnt close connection when body is too long
         # for cl header
-        to_send = tobytes(
-            "GET /long_body HTTP/1.0\r\n"
-            "Connection: Keep-Alive\r\n"
-            "Content-Length: 0\r\n"
-            "\r\n"
+        to_send = (
+            b"GET /long_body HTTP/1.0\r\n"
+            b"Connection: Keep-Alive\r\n"
+            b"Content-Length: 0\r\n"
+            b"\r\n"
         )
         self.connect()
         self.sock.send(to_send)
@@ -813,7 +814,7 @@ class WriteCallbackTests(object):
         content_length = int(headers.get("content-length")) or None
         self.assertEqual(content_length, 9)
         self.assertEqual(content_length, len(response_body))
-        self.assertEqual(response_body, tobytes("abcdefghi"))
+        self.assertEqual(response_body, b"abcdefghi")
         # remote does not close connection (keepalive header)
         self.sock.send(to_send)
         fp = self.sock.makefile("rb", 0)
@@ -823,11 +824,11 @@ class WriteCallbackTests(object):
     def test_equal_body(self):
         # check server doesnt close connection when body is equal to
         # cl header
-        to_send = tobytes(
-            "GET /equal_body HTTP/1.0\r\n"
-            "Connection: Keep-Alive\r\n"
-            "Content-Length: 0\r\n"
-            "\r\n"
+        to_send = (
+            b"GET /equal_body HTTP/1.0\r\n"
+            b"Connection: Keep-Alive\r\n"
+            b"Content-Length: 0\r\n"
+            b"\r\n"
         )
         self.connect()
         self.sock.send(to_send)
@@ -837,7 +838,7 @@ class WriteCallbackTests(object):
         self.assertEqual(content_length, 9)
         self.assertline(line, "200", "OK", "HTTP/1.0")
         self.assertEqual(content_length, len(response_body))
-        self.assertEqual(response_body, tobytes("abcdefghi"))
+        self.assertEqual(response_body, b"abcdefghi")
         # remote does not close connection (keepalive header)
         self.sock.send(to_send)
         fp = self.sock.makefile("rb", 0)
@@ -846,11 +847,11 @@ class WriteCallbackTests(object):
 
     def test_no_content_length(self):
         # wtf happens when there's no content-length
-        to_send = tobytes(
-            "GET /no_content_length HTTP/1.0\r\n"
-            "Connection: Keep-Alive\r\n"
-            "Content-Length: 0\r\n"
-            "\r\n"
+        to_send = (
+            b"GET /no_content_length HTTP/1.0\r\n"
+            b"Connection: Keep-Alive\r\n"
+            b"Content-Length: 0\r\n"
+            b"\r\n"
         )
         self.connect()
         self.sock.send(to_send)
@@ -859,13 +860,13 @@ class WriteCallbackTests(object):
         line, headers, response_body = read_http(fp)
         content_length = headers.get("content-length")
         self.assertEqual(content_length, None)
-        self.assertEqual(response_body, tobytes("abcdefghi"))
+        self.assertEqual(response_body, b"abcdefghi")
         # remote closed connection (despite keepalive header)
         self.send_check_error(to_send)
         self.assertRaises(ConnectionClosed, read_http, fp)
 
 
-class TooLargeTests(object):
+class TooLargeTests:
 
     toobig = 1050
 
@@ -880,10 +881,9 @@ class TooLargeTests(object):
         self.stop_subprocess()
 
     def test_request_body_too_large_with_wrong_cl_http10(self):
-        body = "a" * self.toobig
-        to_send = "GET / HTTP/1.0\r\nContent-Length: 5\r\n\r\n"
+        body = b"a" * self.toobig
+        to_send = b"GET / HTTP/1.0\r\nContent-Length: 5\r\n\r\n"
         to_send += body
-        to_send = tobytes(to_send)
         self.connect()
         self.sock.send(to_send)
         fp = self.sock.makefile("rb")
@@ -899,12 +899,11 @@ class TooLargeTests(object):
         self.assertRaises(ConnectionClosed, read_http, fp)
 
     def test_request_body_too_large_with_wrong_cl_http10_keepalive(self):
-        body = "a" * self.toobig
+        body = b"a" * self.toobig
         to_send = (
-            "GET / HTTP/1.0\r\nContent-Length: 5\r\nConnection: Keep-Alive\r\n\r\n"
+            b"GET / HTTP/1.0\r\nContent-Length: 5\r\nConnection: Keep-Alive\r\n\r\n"
         )
         to_send += body
-        to_send = tobytes(to_send)
         self.connect()
         self.sock.send(to_send)
         fp = self.sock.makefile("rb")
@@ -922,10 +921,9 @@ class TooLargeTests(object):
         self.assertRaises(ConnectionClosed, read_http, fp)
 
     def test_request_body_too_large_with_no_cl_http10(self):
-        body = "a" * self.toobig
-        to_send = "GET / HTTP/1.0\r\n\r\n"
+        body = b"a" * self.toobig
+        to_send = b"GET / HTTP/1.0\r\n\r\n"
         to_send += body
-        to_send = tobytes(to_send)
         self.connect()
         self.sock.send(to_send)
         fp = self.sock.makefile("rb", 0)
@@ -938,10 +936,9 @@ class TooLargeTests(object):
         self.assertRaises(ConnectionClosed, read_http, fp)
 
     def test_request_body_too_large_with_no_cl_http10_keepalive(self):
-        body = "a" * self.toobig
-        to_send = "GET / HTTP/1.0\r\nConnection: Keep-Alive\r\n\r\n"
+        body = b"a" * self.toobig
+        to_send = b"GET / HTTP/1.0\r\nConnection: Keep-Alive\r\n\r\n"
         to_send += body
-        to_send = tobytes(to_send)
         self.connect()
         self.sock.send(to_send)
         fp = self.sock.makefile("rb", 0)
@@ -961,10 +958,9 @@ class TooLargeTests(object):
         self.assertRaises(ConnectionClosed, read_http, fp)
 
     def test_request_body_too_large_with_wrong_cl_http11(self):
-        body = "a" * self.toobig
-        to_send = "GET / HTTP/1.1\r\nContent-Length: 5\r\n\r\n"
+        body = b"a" * self.toobig
+        to_send = b"GET / HTTP/1.1\r\nContent-Length: 5\r\n\r\n"
         to_send += body
-        to_send = tobytes(to_send)
         self.connect()
         self.sock.send(to_send)
         fp = self.sock.makefile("rb")
@@ -983,10 +979,9 @@ class TooLargeTests(object):
         self.assertRaises(ConnectionClosed, read_http, fp)
 
     def test_request_body_too_large_with_wrong_cl_http11_connclose(self):
-        body = "a" * self.toobig
-        to_send = "GET / HTTP/1.1\r\nContent-Length: 5\r\nConnection: close\r\n\r\n"
+        body = b"a" * self.toobig
+        to_send = b"GET / HTTP/1.1\r\nContent-Length: 5\r\nConnection: close\r\n\r\n"
         to_send += body
-        to_send = tobytes(to_send)
         self.connect()
         self.sock.send(to_send)
         fp = self.sock.makefile("rb", 0)
@@ -1000,10 +995,9 @@ class TooLargeTests(object):
         self.assertRaises(ConnectionClosed, read_http, fp)
 
     def test_request_body_too_large_with_no_cl_http11(self):
-        body = "a" * self.toobig
-        to_send = "GET / HTTP/1.1\r\n\r\n"
+        body = b"a" * self.toobig
+        to_send = b"GET / HTTP/1.1\r\n\r\n"
         to_send += body
-        to_send = tobytes(to_send)
         self.connect()
         self.sock.send(to_send)
         fp = self.sock.makefile("rb")
@@ -1025,10 +1019,9 @@ class TooLargeTests(object):
         self.assertRaises(ConnectionClosed, read_http, fp)
 
     def test_request_body_too_large_with_no_cl_http11_connclose(self):
-        body = "a" * self.toobig
-        to_send = "GET / HTTP/1.1\r\nConnection: close\r\n\r\n"
+        body = b"a" * self.toobig
+        to_send = b"GET / HTTP/1.1\r\nConnection: close\r\n\r\n"
         to_send += body
-        to_send = tobytes(to_send)
         self.connect()
         self.sock.send(to_send)
         fp = self.sock.makefile("rb", 0)
@@ -1042,12 +1035,11 @@ class TooLargeTests(object):
         self.assertRaises(ConnectionClosed, read_http, fp)
 
     def test_request_body_too_large_chunked_encoding(self):
-        control_line = "20;\r\n"  # 20 hex = 32 dec
-        s = "This string has 32 characters.\r\n"
-        to_send = "GET / HTTP/1.1\r\nTransfer-Encoding: chunked\r\n\r\n"
+        control_line = b"20;\r\n"  # 20 hex = 32 dec
+        s = b"This string has 32 characters.\r\n"
+        to_send = b"GET / HTTP/1.1\r\nTransfer-Encoding: chunked\r\n\r\n"
         repeat = control_line + s
         to_send += repeat * ((self.toobig // len(repeat)) + 1)
-        to_send = tobytes(to_send)
         self.connect()
         self.sock.send(to_send)
         fp = self.sock.makefile("rb", 0)
@@ -1062,7 +1054,7 @@ class TooLargeTests(object):
         self.assertRaises(ConnectionClosed, read_http, fp)
 
 
-class InternalServerErrorTests(object):
+class InternalServerErrorTests:
     def setUp(self):
         from tests.fixtureapps import error
 
@@ -1072,8 +1064,7 @@ class InternalServerErrorTests(object):
         self.stop_subprocess()
 
     def test_before_start_response_http_10(self):
-        to_send = "GET /before_start_response HTTP/1.0\r\n\r\n"
-        to_send = tobytes(to_send)
+        to_send = b"GET /before_start_response HTTP/1.0\r\n\r\n"
         self.connect()
         self.sock.send(to_send)
         fp = self.sock.makefile("rb", 0)
@@ -1088,8 +1079,7 @@ class InternalServerErrorTests(object):
         self.assertRaises(ConnectionClosed, read_http, fp)
 
     def test_before_start_response_http_11(self):
-        to_send = "GET /before_start_response HTTP/1.1\r\n\r\n"
-        to_send = tobytes(to_send)
+        to_send = b"GET /before_start_response HTTP/1.1\r\n\r\n"
         self.connect()
         self.sock.send(to_send)
         fp = self.sock.makefile("rb", 0)
@@ -1107,9 +1097,7 @@ class InternalServerErrorTests(object):
         self.assertRaises(ConnectionClosed, read_http, fp)
 
     def test_before_start_response_http_11_close(self):
-        to_send = tobytes(
-            "GET /before_start_response HTTP/1.1\r\nConnection: close\r\n\r\n"
-        )
+        to_send = b"GET /before_start_response HTTP/1.1\r\nConnection: close\r\n\r\n"
         self.connect()
         self.sock.send(to_send)
         fp = self.sock.makefile("rb", 0)
@@ -1128,8 +1116,7 @@ class InternalServerErrorTests(object):
         self.assertRaises(ConnectionClosed, read_http, fp)
 
     def test_after_start_response_http10(self):
-        to_send = "GET /after_start_response HTTP/1.0\r\n\r\n"
-        to_send = tobytes(to_send)
+        to_send = b"GET /after_start_response HTTP/1.0\r\n\r\n"
         self.connect()
         self.sock.send(to_send)
         fp = self.sock.makefile("rb", 0)
@@ -1148,8 +1135,7 @@ class InternalServerErrorTests(object):
         self.assertRaises(ConnectionClosed, read_http, fp)
 
     def test_after_start_response_http11(self):
-        to_send = "GET /after_start_response HTTP/1.1\r\n\r\n"
-        to_send = tobytes(to_send)
+        to_send = b"GET /after_start_response HTTP/1.1\r\n\r\n"
         self.connect()
         self.sock.send(to_send)
         fp = self.sock.makefile("rb", 0)
@@ -1167,9 +1153,7 @@ class InternalServerErrorTests(object):
         self.assertRaises(ConnectionClosed, read_http, fp)
 
     def test_after_start_response_http11_close(self):
-        to_send = tobytes(
-            "GET /after_start_response HTTP/1.1\r\nConnection: close\r\n\r\n"
-        )
+        to_send = b"GET /after_start_response HTTP/1.1\r\nConnection: close\r\n\r\n"
         self.connect()
         self.sock.send(to_send)
         fp = self.sock.makefile("rb", 0)
@@ -1188,8 +1172,7 @@ class InternalServerErrorTests(object):
         self.assertRaises(ConnectionClosed, read_http, fp)
 
     def test_after_write_cb(self):
-        to_send = "GET /after_write_cb HTTP/1.1\r\n\r\n"
-        to_send = tobytes(to_send)
+        to_send = b"GET /after_write_cb HTTP/1.1\r\n\r\n"
         self.connect()
         self.sock.send(to_send)
         fp = self.sock.makefile("rb", 0)
@@ -1201,8 +1184,7 @@ class InternalServerErrorTests(object):
         self.assertRaises(ConnectionClosed, read_http, fp)
 
     def test_in_generator(self):
-        to_send = "GET /in_generator HTTP/1.1\r\n\r\n"
-        to_send = tobytes(to_send)
+        to_send = b"GET /in_generator HTTP/1.1\r\n\r\n"
         self.connect()
         self.sock.send(to_send)
         fp = self.sock.makefile("rb", 0)
@@ -1214,7 +1196,7 @@ class InternalServerErrorTests(object):
         self.assertRaises(ConnectionClosed, read_http, fp)
 
 
-class FileWrapperTests(object):
+class FileWrapperTests:
     def setUp(self):
         from tests.fixtureapps import filewrapper
 
@@ -1224,8 +1206,7 @@ class FileWrapperTests(object):
         self.stop_subprocess()
 
     def test_filelike_http11(self):
-        to_send = "GET /filelike HTTP/1.1\r\n\r\n"
-        to_send = tobytes(to_send)
+        to_send = b"GET /filelike HTTP/1.1\r\n\r\n"
 
         self.connect()
 
@@ -1242,8 +1223,7 @@ class FileWrapperTests(object):
             # connection has not been closed
 
     def test_filelike_nocl_http11(self):
-        to_send = "GET /filelike_nocl HTTP/1.1\r\n\r\n"
-        to_send = tobytes(to_send)
+        to_send = b"GET /filelike_nocl HTTP/1.1\r\n\r\n"
 
         self.connect()
 
@@ -1260,8 +1240,7 @@ class FileWrapperTests(object):
             # connection has not been closed
 
     def test_filelike_shortcl_http11(self):
-        to_send = "GET /filelike_shortcl HTTP/1.1\r\n\r\n"
-        to_send = tobytes(to_send)
+        to_send = b"GET /filelike_shortcl HTTP/1.1\r\n\r\n"
 
         self.connect()
 
@@ -1279,8 +1258,7 @@ class FileWrapperTests(object):
             # connection has not been closed
 
     def test_filelike_longcl_http11(self):
-        to_send = "GET /filelike_longcl HTTP/1.1\r\n\r\n"
-        to_send = tobytes(to_send)
+        to_send = b"GET /filelike_longcl HTTP/1.1\r\n\r\n"
 
         self.connect()
 
@@ -1297,8 +1275,7 @@ class FileWrapperTests(object):
             # connection has not been closed
 
     def test_notfilelike_http11(self):
-        to_send = "GET /notfilelike HTTP/1.1\r\n\r\n"
-        to_send = tobytes(to_send)
+        to_send = b"GET /notfilelike HTTP/1.1\r\n\r\n"
 
         self.connect()
 
@@ -1315,8 +1292,7 @@ class FileWrapperTests(object):
             # connection has not been closed
 
     def test_notfilelike_iobase_http11(self):
-        to_send = "GET /notfilelike_iobase HTTP/1.1\r\n\r\n"
-        to_send = tobytes(to_send)
+        to_send = b"GET /notfilelike_iobase HTTP/1.1\r\n\r\n"
 
         self.connect()
 
@@ -1333,8 +1309,7 @@ class FileWrapperTests(object):
             # connection has not been closed
 
     def test_notfilelike_nocl_http11(self):
-        to_send = "GET /notfilelike_nocl HTTP/1.1\r\n\r\n"
-        to_send = tobytes(to_send)
+        to_send = b"GET /notfilelike_nocl HTTP/1.1\r\n\r\n"
 
         self.connect()
 
@@ -1350,8 +1325,7 @@ class FileWrapperTests(object):
         self.assertRaises(ConnectionClosed, read_http, fp)
 
     def test_notfilelike_shortcl_http11(self):
-        to_send = "GET /notfilelike_shortcl HTTP/1.1\r\n\r\n"
-        to_send = tobytes(to_send)
+        to_send = b"GET /notfilelike_shortcl HTTP/1.1\r\n\r\n"
 
         self.connect()
 
@@ -1369,8 +1343,7 @@ class FileWrapperTests(object):
             # connection has not been closed
 
     def test_notfilelike_longcl_http11(self):
-        to_send = "GET /notfilelike_longcl HTTP/1.1\r\n\r\n"
-        to_send = tobytes(to_send)
+        to_send = b"GET /notfilelike_longcl HTTP/1.1\r\n\r\n"
 
         self.connect()
 
@@ -1388,8 +1361,7 @@ class FileWrapperTests(object):
         self.assertRaises(ConnectionClosed, read_http, fp)
 
     def test_filelike_http10(self):
-        to_send = "GET /filelike HTTP/1.0\r\n\r\n"
-        to_send = tobytes(to_send)
+        to_send = b"GET /filelike HTTP/1.0\r\n\r\n"
 
         self.connect()
 
@@ -1407,8 +1379,7 @@ class FileWrapperTests(object):
         self.assertRaises(ConnectionClosed, read_http, fp)
 
     def test_filelike_nocl_http10(self):
-        to_send = "GET /filelike_nocl HTTP/1.0\r\n\r\n"
-        to_send = tobytes(to_send)
+        to_send = b"GET /filelike_nocl HTTP/1.0\r\n\r\n"
 
         self.connect()
 
@@ -1426,8 +1397,7 @@ class FileWrapperTests(object):
         self.assertRaises(ConnectionClosed, read_http, fp)
 
     def test_notfilelike_http10(self):
-        to_send = "GET /notfilelike HTTP/1.0\r\n\r\n"
-        to_send = tobytes(to_send)
+        to_send = b"GET /notfilelike HTTP/1.0\r\n\r\n"
 
         self.connect()
 
@@ -1445,8 +1415,7 @@ class FileWrapperTests(object):
         self.assertRaises(ConnectionClosed, read_http, fp)
 
     def test_notfilelike_nocl_http10(self):
-        to_send = "GET /notfilelike_nocl HTTP/1.0\r\n\r\n"
-        to_send = tobytes(to_send)
+        to_send = b"GET /notfilelike_nocl HTTP/1.0\r\n\r\n"
 
         self.connect()
 
@@ -1512,7 +1481,7 @@ if hasattr(socket, "AF_UNIX"):
             # Coverage doesn't see this as it's ran in a separate process.
             # To permit parallel testing, use a PID-dependent socket.
             kw["unix_socket"] = "/tmp/waitress.test-%d.sock" % os.getpid()
-            super(FixtureUnixWSGIServer, self).__init__(application, **kw)
+            super().__init__(application, **kw)
             queue.put(self.socket.getsockname())
 
     class UnixTests(SubprocessTests):
@@ -1523,7 +1492,7 @@ if hasattr(socket, "AF_UNIX"):
             return UnixHTTPConnection(self.bound_to)
 
         def stop_subprocess(self):
-            super(UnixTests, self).stop_subprocess()
+            super().stop_subprocess()
             cleanup_unix_socket(self.bound_to)
 
         def send_check_error(self, to_send):
@@ -1531,8 +1500,9 @@ if hasattr(socket, "AF_UNIX"):
             # 'Broken pipe' error when the socket it closed.
             try:
                 self.sock.send(to_send)
-            except socket.error as exc:
-                self.assertEqual(get_errno(exc), errno.EPIPE)
+            except OSError as exc:
+                valid_errors = {errno.EPIPE, errno.ENOTCONN}
+                self.assertIn(get_errno(exc), valid_errors)
 
     class UnixEchoTests(EchoTests, UnixTests, unittest.TestCase):
         pass
@@ -1570,13 +1540,16 @@ def parse_headers(fp):
     """Parses only RFC2822 headers from a file pointer.
     """
     headers = {}
+
     while True:
         line = fp.readline()
+
         if line in (b"\r\n", b"\n", b""):
             break
         line = line.decode("iso-8859-1")
         name, value = line.strip().split(":", 1)
         headers[name.lower().strip()] = value.lower().strip()
+
     return headers
 
 
@@ -1602,25 +1575,31 @@ class ConnectionClosed(Exception):
 def read_http(fp):  # pragma: no cover
     try:
         response_line = fp.readline()
-    except socket.error as exc:
+    except OSError as exc:
         fp.close()
         # errno 104 is ENOTRECOVERABLE, In WinSock 10054 is ECONNRESET
+
         if get_errno(exc) in (errno.ECONNABORTED, errno.ECONNRESET, 104, 10054):
             raise ConnectionClosed
         raise
+
     if not response_line:
         raise ConnectionClosed
 
     header_lines = []
+
     while True:
         line = fp.readline()
+
         if line in (b"\r\n", b"\r\n", b""):
             break
         else:
             header_lines.append(line)
     headers = dict()
+
     for x in header_lines:
         x = x.strip()
+
         if not x:
             continue
         key, value = x.split(b": ", 1)
@@ -1633,8 +1612,10 @@ def read_http(fp):  # pragma: no cover
         num = int(headers["content-length"])
         body = b""
         left = num
+
         while left > 0:
             data = fp.read(left)
+
             if not data:
                 break
             body += data
@@ -1670,5 +1651,6 @@ def get_errno(exc):  # pragma: no cover
 def chunks(l, n):
     """ Yield successive n-sized chunks from l.
     """
+
     for i in range(0, len(l), n):
         yield l[i : i + n]
diff --git a/tests/test_init.py b/tests/test_init.py
index f9b91d7..c824c21 100644
--- a/tests/test_init.py
+++ b/tests/test_init.py
@@ -31,7 +31,7 @@ class Test_serve_paste(unittest.TestCase):
         self.assertEqual(server.ran, True)
 
 
-class DummyServerFactory(object):
+class DummyServerFactory:
     ran = False
 
     def __call__(self, app, **kw):
@@ -44,7 +44,7 @@ class DummyServerFactory(object):
         self.ran = True
 
 
-class DummyAdj(object):
+class DummyAdj:
     verbose = False
 
     def __init__(self, kw):
diff --git a/tests/test_parser.py b/tests/test_parser.py
index 91837c7..eace4af 100644
--- a/tests/test_parser.py
+++ b/tests/test_parser.py
@@ -15,13 +15,26 @@
 """
 import unittest
 
-from waitress.compat import text_, tobytes
+from waitress.adjustments import Adjustments
+from waitress.parser import (
+    HTTPRequestParser,
+    ParsingError,
+    TransferEncodingNotImplemented,
+    crack_first_line,
+    get_header_lines,
+    split_uri,
+    unquote_bytes_to_wsgi,
+)
+from waitress.utilities import (
+    BadRequest,
+    RequestEntityTooLarge,
+    RequestHeaderFieldsTooLarge,
+    ServerNotImplemented,
+)
 
 
 class TestHTTPRequestParser(unittest.TestCase):
     def setUp(self):
-        from waitress.parser import HTTPRequestParser
-        from waitress.adjustments import Adjustments
 
         my_adj = Adjustments()
         self.parser = HTTPRequestParser(my_adj)
@@ -45,8 +58,6 @@ class TestHTTPRequestParser(unittest.TestCase):
         self.assertEqual(self.parser.headers, {})
 
     def test_received_bad_host_header(self):
-        from waitress.utilities import BadRequest
-
         data = b"HTTP/1.0 GET /foobar\r\n Host: foo\r\n\r\n"
         result = self.parser.received(data)
         self.assertEqual(result, 36)
@@ -54,8 +65,6 @@ class TestHTTPRequestParser(unittest.TestCase):
         self.assertEqual(self.parser.error.__class__, BadRequest)
 
     def test_received_bad_transfer_encoding(self):
-        from waitress.utilities import ServerNotImplemented
-
         data = (
             b"GET /foobar HTTP/1.1\r\n"
             b"Transfer-Encoding: foo\r\n"
@@ -89,7 +98,6 @@ class TestHTTPRequestParser(unittest.TestCase):
         self.assertEqual(result, 0)
 
     def test_received_cl_too_large(self):
-        from waitress.utilities import RequestEntityTooLarge
 
         self.parser.adj.max_request_body_size = 2
         data = b"GET /foobar HTTP/8.4\r\nContent-Length: 10\r\n\r\n"
@@ -99,7 +107,6 @@ class TestHTTPRequestParser(unittest.TestCase):
         self.assertTrue(isinstance(self.parser.error, RequestEntityTooLarge))
 
     def test_received_headers_too_large(self):
-        from waitress.utilities import RequestHeaderFieldsTooLarge
 
         self.parser.adj.max_request_header_size = 2
         data = b"GET /foobar HTTP/8.4\r\nX-Foo: 1\r\n\r\n"
@@ -109,8 +116,6 @@ class TestHTTPRequestParser(unittest.TestCase):
         self.assertTrue(isinstance(self.parser.error, RequestHeaderFieldsTooLarge))
 
     def test_received_body_too_large(self):
-        from waitress.utilities import RequestEntityTooLarge
-
         self.parser.adj.max_request_body_size = 2
         data = (
             b"GET /foobar HTTP/1.1\r\n"
@@ -129,8 +134,6 @@ class TestHTTPRequestParser(unittest.TestCase):
         self.assertTrue(isinstance(self.parser.error, RequestEntityTooLarge))
 
     def test_received_error_from_parser(self):
-        from waitress.utilities import BadRequest
-
         data = (
             b"GET /foobar HTTP/1.1\r\n"
             b"Transfer-Encoding: chunked\r\n"
@@ -171,8 +174,6 @@ class TestHTTPRequestParser(unittest.TestCase):
         self.assertEqual(self.parser.headers["FOO"], "bar")
 
     def test_parse_header_no_cr_in_headerplus(self):
-        from waitress.parser import ParsingError
-
         data = b"GET /foobar HTTP/8.4"
 
         try:
@@ -183,8 +184,6 @@ class TestHTTPRequestParser(unittest.TestCase):
             self.assertTrue(False)
 
     def test_parse_header_bad_content_length(self):
-        from waitress.parser import ParsingError
-
         data = b"GET /foobar HTTP/8.4\r\ncontent-length: abc\r\n"
 
         try:
@@ -195,8 +194,6 @@ class TestHTTPRequestParser(unittest.TestCase):
             self.assertTrue(False)
 
     def test_parse_header_multiple_content_length(self):
-        from waitress.parser import ParsingError
-
         data = b"GET /foobar HTTP/8.4\r\ncontent-length: 10\r\ncontent-length: 20\r\n"
 
         try:
@@ -213,8 +210,6 @@ class TestHTTPRequestParser(unittest.TestCase):
         self.assertEqual(self.parser.body_rcv.__class__.__name__, "ChunkedReceiver")
 
     def test_parse_header_transfer_encoding_invalid(self):
-        from waitress.parser import TransferEncodingNotImplemented
-
         data = b"GET /foobar HTTP/1.1\r\ntransfer-encoding: gzip\r\n"
 
         try:
@@ -225,7 +220,6 @@ class TestHTTPRequestParser(unittest.TestCase):
             self.assertTrue(False)
 
     def test_parse_header_transfer_encoding_invalid_multiple(self):
-        from waitress.parser import TransferEncodingNotImplemented
 
         data = b"GET /foobar HTTP/1.1\r\ntransfer-encoding: gzip\r\ntransfer-encoding: chunked\r\n"
 
@@ -237,8 +231,6 @@ class TestHTTPRequestParser(unittest.TestCase):
             self.assertTrue(False)
 
     def test_parse_header_transfer_encoding_invalid_whitespace(self):
-        from waitress.parser import TransferEncodingNotImplemented
-
         data = b"GET /foobar HTTP/1.1\r\nTransfer-Encoding:\x85chunked\r\n"
 
         try:
@@ -249,8 +241,6 @@ class TestHTTPRequestParser(unittest.TestCase):
             self.assertTrue(False)
 
     def test_parse_header_transfer_encoding_invalid_unicode(self):
-        from waitress.parser import TransferEncodingNotImplemented
-
         # This is the binary encoding for the UTF-8 character
         # https://www.compart.com/en/unicode/U+212A "unicode character "K""
         # which if waitress were to accidentally do the wrong thing get
@@ -286,8 +276,6 @@ class TestHTTPRequestParser(unittest.TestCase):
         self.parser.close()  # doesn't raise
 
     def test_parse_header_lf_only(self):
-        from waitress.parser import ParsingError
-
         data = b"GET /foobar HTTP/8.4\nfoo: bar"
 
         try:
@@ -298,8 +286,6 @@ class TestHTTPRequestParser(unittest.TestCase):
             self.assertTrue(False)
 
     def test_parse_header_cr_only(self):
-        from waitress.parser import ParsingError
-
         data = b"GET /foobar HTTP/8.4\rfoo: bar"
         try:
             self.parser.parse_header(data)
@@ -309,8 +295,6 @@ class TestHTTPRequestParser(unittest.TestCase):
             self.assertTrue(False)
 
     def test_parse_header_extra_lf_in_header(self):
-        from waitress.parser import ParsingError
-
         data = b"GET /foobar HTTP/8.4\r\nfoo: \nbar\r\n"
         try:
             self.parser.parse_header(data)
@@ -320,8 +304,6 @@ class TestHTTPRequestParser(unittest.TestCase):
             self.assertTrue(False)
 
     def test_parse_header_extra_lf_in_first_line(self):
-        from waitress.parser import ParsingError
-
         data = b"GET /foobar\n HTTP/8.4\r\n"
         try:
             self.parser.parse_header(data)
@@ -331,8 +313,6 @@ class TestHTTPRequestParser(unittest.TestCase):
             self.assertTrue(False)
 
     def test_parse_header_invalid_whitespace(self):
-        from waitress.parser import ParsingError
-
         data = b"GET /foobar HTTP/8.4\r\nfoo : bar\r\n"
         try:
             self.parser.parse_header(data)
@@ -342,8 +322,6 @@ class TestHTTPRequestParser(unittest.TestCase):
             self.assertTrue(False)
 
     def test_parse_header_invalid_whitespace_vtab(self):
-        from waitress.parser import ParsingError
-
         data = b"GET /foobar HTTP/1.1\r\nfoo:\x0bbar\r\n"
         try:
             self.parser.parse_header(data)
@@ -353,8 +331,6 @@ class TestHTTPRequestParser(unittest.TestCase):
             self.assertTrue(False)
 
     def test_parse_header_invalid_no_colon(self):
-        from waitress.parser import ParsingError
-
         data = b"GET /foobar HTTP/1.1\r\nfoo: bar\r\nnotvalid\r\n"
         try:
             self.parser.parse_header(data)
@@ -364,8 +340,6 @@ class TestHTTPRequestParser(unittest.TestCase):
             self.assertTrue(False)
 
     def test_parse_header_invalid_folding_spacing(self):
-        from waitress.parser import ParsingError
-
         data = b"GET /foobar HTTP/1.1\r\nfoo: bar\r\n\t\x0bbaz\r\n"
         try:
             self.parser.parse_header(data)
@@ -375,8 +349,6 @@ class TestHTTPRequestParser(unittest.TestCase):
             self.assertTrue(False)
 
     def test_parse_header_invalid_chars(self):
-        from waitress.parser import ParsingError
-
         data = b"GET /foobar HTTP/1.1\r\nfoo: bar\r\nfoo: \x0bbaz\r\n"
         try:
             self.parser.parse_header(data)
@@ -386,8 +358,6 @@ class TestHTTPRequestParser(unittest.TestCase):
             self.assertTrue(False)
 
     def test_parse_header_empty(self):
-        from waitress.parser import ParsingError
-
         data = b"GET /foobar HTTP/1.1\r\nfoo: bar\r\nempty:\r\n"
         self.parser.parse_header(data)
 
@@ -397,8 +367,6 @@ class TestHTTPRequestParser(unittest.TestCase):
         self.assertEqual(self.parser.headers["FOO"], "bar")
 
     def test_parse_header_multiple_values(self):
-        from waitress.parser import ParsingError
-
         data = b"GET /foobar HTTP/1.1\r\nfoo: bar, whatever, more, please, yes\r\n"
         self.parser.parse_header(data)
 
@@ -406,8 +374,6 @@ class TestHTTPRequestParser(unittest.TestCase):
         self.assertEqual(self.parser.headers["FOO"], "bar, whatever, more, please, yes")
 
     def test_parse_header_multiple_values_header_folded(self):
-        from waitress.parser import ParsingError
-
         data = b"GET /foobar HTTP/1.1\r\nfoo: bar, whatever,\r\n more, please, yes\r\n"
         self.parser.parse_header(data)
 
@@ -415,8 +381,6 @@ class TestHTTPRequestParser(unittest.TestCase):
         self.assertEqual(self.parser.headers["FOO"], "bar, whatever, more, please, yes")
 
     def test_parse_header_multiple_values_header_folded_multiple(self):
-        from waitress.parser import ParsingError
-
         data = b"GET /foobar HTTP/1.1\r\nfoo: bar, whatever,\r\n more\r\nfoo: please, yes\r\n"
         self.parser.parse_header(data)
 
@@ -425,8 +389,6 @@ class TestHTTPRequestParser(unittest.TestCase):
 
     def test_parse_header_multiple_values_extra_space(self):
         # Tests errata from: https://www.rfc-editor.org/errata_search.php?rfc=7230&eid=4189
-        from waitress.parser import ParsingError
-
         data = b"GET /foobar HTTP/1.1\r\nfoo: abrowser/0.001 (C O M M E N T)\r\n"
         self.parser.parse_header(data)
 
@@ -434,8 +396,6 @@ class TestHTTPRequestParser(unittest.TestCase):
         self.assertEqual(self.parser.headers["FOO"], "abrowser/0.001 (C O M M E N T)")
 
     def test_parse_header_invalid_backtrack_bad(self):
-        from waitress.parser import ParsingError
-
         data = b"GET /foobar HTTP/1.1\r\nfoo: bar\r\nfoo: xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx\x10\r\n"
         try:
             self.parser.parse_header(data)
@@ -445,8 +405,6 @@ class TestHTTPRequestParser(unittest.TestCase):
             self.assertTrue(False)
 
     def test_parse_header_short_values(self):
-        from waitress.parser import ParsingError
-
         data = b"GET /foobar HTTP/1.1\r\none: 1\r\ntwo: 22\r\n"
         self.parser.parse_header(data)
 
@@ -458,8 +416,6 @@ class TestHTTPRequestParser(unittest.TestCase):
 
 class Test_split_uri(unittest.TestCase):
     def _callFUT(self, uri):
-        from waitress.parser import split_uri
-
         (
             self.proxy_scheme,
             self.proxy_netloc,
@@ -499,7 +455,6 @@ class Test_split_uri(unittest.TestCase):
 
     def test_split_uri_unicode_error_raises_parsing_error(self):
         # See https://github.com/Pylons/waitress/issues/64
-        from waitress.parser import ParsingError
 
         # Either pass or throw a ParsingError, just don't throw another type of
         # exception as that will cause the connection to close badly:
@@ -535,8 +490,6 @@ class Test_split_uri(unittest.TestCase):
 
 class Test_get_header_lines(unittest.TestCase):
     def _callFUT(self, data):
-        from waitress.parser import get_header_lines
-
         return get_header_lines(data)
 
     def test_get_header_lines(self):
@@ -561,15 +514,11 @@ class Test_get_header_lines(unittest.TestCase):
 
     def test_get_header_lines_malformed(self):
         # https://corte.si/posts/code/pathod/pythonservers/index.html
-        from waitress.parser import ParsingError
-
         self.assertRaises(ParsingError, self._callFUT, b" Host: localhost\r\n\r\n")
 
 
 class Test_crack_first_line(unittest.TestCase):
     def _callFUT(self, line):
-        from waitress.parser import crack_first_line
-
         return crack_first_line(line)
 
     def test_crack_first_line_matchok(self):
@@ -577,8 +526,6 @@ class Test_crack_first_line(unittest.TestCase):
         self.assertEqual(result, (b"GET", b"/", b"1.0"))
 
     def test_crack_first_line_lowercase_method(self):
-        from waitress.parser import ParsingError
-
         self.assertRaises(ParsingError, self._callFUT, b"get / HTTP/1.0")
 
     def test_crack_first_line_nomatch(self):
@@ -595,9 +542,6 @@ class Test_crack_first_line(unittest.TestCase):
 
 class TestHTTPRequestParserIntegration(unittest.TestCase):
     def setUp(self):
-        from waitress.parser import HTTPRequestParser
-        from waitress.adjustments import Adjustments
-
         my_adj = Adjustments()
         self.parser = HTTPRequestParser(my_adj)
 
@@ -657,8 +601,8 @@ class TestHTTPRequestParserIntegration(unittest.TestCase):
         )
         # path should be utf-8 encoded
         self.assertEqual(
-            tobytes(parser.path).decode("utf-8"),
-            text_(b"/foo/a++/\xc3\xa4=&a:int", "utf-8"),
+            parser.path.encode("latin-1").decode("utf-8"),
+            b"/foo/a++/\xc3\xa4=&a:int".decode("utf-8"),
         )
         self.assertEqual(
             parser.query, "d=b+%2B%2F%3D%26b%3Aint&c+%2B%2F%3D%26c%3Aint=6"
@@ -721,7 +665,19 @@ class TestHTTPRequestParserIntegration(unittest.TestCase):
         self.assertEqual(self.parser.headers, {"CONTENT_LENGTH": "6",})
 
 
-class DummyBodyStream(object):
+class Test_unquote_bytes_to_wsgi(unittest.TestCase):
+    def _callFUT(self, v):
+
+        return unquote_bytes_to_wsgi(v)
+
+    def test_highorder(self):
+        val = b"/a%C5%9B"
+        result = self._callFUT(val)
+        # PEP 3333 urlunquoted-latin1-decoded-bytes
+        self.assertEqual(result, "/aÅ\x9b")
+
+
+class DummyBodyStream:
     def getfile(self):
         return self
 
diff --git a/tests/test_proxy_headers.py b/tests/test_proxy_headers.py
index 15b4a08..e6f0ed6 100644
--- a/tests/test_proxy_headers.py
+++ b/tests/test_proxy_headers.py
@@ -1,7 +1,5 @@
 import unittest
 
-from waitress.compat import tobytes
-
 
 class TestProxyHeadersMiddleware(unittest.TestCase):
     def _makeOne(self, app, **kw):
@@ -18,7 +16,7 @@ class TestProxyHeadersMiddleware(unittest.TestCase):
             response.headers = response_headers
 
         response.steps = list(app(environ, start_response))
-        response.body = b"".join(tobytes(s) for s in response.steps)
+        response.body = b"".join(s.encode("latin-1") for s in response.steps)
         return response
 
     def test_get_environment_values_w_scheme_override_untrusted(self):
@@ -681,7 +679,7 @@ class TestProxyHeadersMiddleware(unittest.TestCase):
         self.assertIn(b'Header "X-Forwarded-Host" malformed', response.body)
 
 
-class DummyLogger(object):
+class DummyLogger:
     def __init__(self):
         self.logged = []
 
@@ -689,14 +687,14 @@ class DummyLogger(object):
         self.logged.append(msg % args)
 
 
-class DummyApp(object):
+class DummyApp:
     def __call__(self, environ, start_response):
         self.environ = environ
         start_response("200 OK", [("Content-Type", "text/plain")])
         yield "hello"
 
 
-class DummyResponse(object):
+class DummyResponse:
     status = None
     headers = None
     body = None
diff --git a/tests/test_receiver.py b/tests/test_receiver.py
index b4910bb..f55aa68 100644
--- a/tests/test_receiver.py
+++ b/tests/test_receiver.py
@@ -226,7 +226,7 @@ class TestChunkedReceiver(unittest.TestCase):
         self.assertEqual(inst.error, None)
 
 
-class DummyBuffer(object):
+class DummyBuffer:
     def __init__(self, data=None):
         if data is None:
             data = []
diff --git a/tests/test_runner.py b/tests/test_runner.py
index e53018b..4cf6f6f 100644
--- a/tests/test_runner.py
+++ b/tests/test_runner.py
@@ -12,17 +12,17 @@ from waitress import runner
 
 class Test_match(unittest.TestCase):
     def test_empty(self):
-        self.assertRaisesRegexp(
+        self.assertRaisesRegex(
             ValueError, "^Malformed application ''$", runner.match, ""
         )
 
     def test_module_only(self):
-        self.assertRaisesRegexp(
+        self.assertRaisesRegex(
             ValueError, r"^Malformed application 'foo\.bar'$", runner.match, "foo.bar"
         )
 
     def test_bad_module(self):
-        self.assertRaisesRegexp(
+        self.assertRaisesRegex(
             ValueError,
             r"^Malformed application 'foo#bar:barney'$",
             runner.match,
@@ -42,7 +42,7 @@ class Test_resolve(unittest.TestCase):
         )
 
     def test_nonexistent_function(self):
-        self.assertRaisesRegexp(
+        self.assertRaisesRegex(
             AttributeError,
             r"has no attribute 'nonexistent_function'",
             runner.resolve,
@@ -57,7 +57,7 @@ class Test_resolve(unittest.TestCase):
 
     def test_complex_happy_path(self):
         # Ensure we can recursively resolve object attributes if necessary.
-        self.assertEquals(runner.resolve("os.path", "exists.__name__"), "exists")
+        self.assertEqual(runner.resolve("os.path", "exists.__name__"), "exists")
 
 
 class Test_run(unittest.TestCase):
@@ -65,7 +65,7 @@ class Test_run(unittest.TestCase):
         argv = ["waitress-serve"] + argv
         with capture() as captured:
             self.assertEqual(runner.run(argv=argv), code)
-        self.assertRegexpMatches(captured.getvalue(), regex)
+        self.assertRegex(captured.getvalue(), regex)
         captured.close()
 
     def test_bad(self):
@@ -119,7 +119,7 @@ class Test_run(unittest.TestCase):
         )
 
     def test_simple_call(self):
-        import tests.fixtureapps.runner as _apps
+        from tests.fixtureapps import runner as _apps
 
         def check_server(app, **kw):
             self.assertIs(app, _apps.app)
@@ -133,7 +133,7 @@ class Test_run(unittest.TestCase):
         self.assertEqual(runner.run(argv=argv, _serve=check_server), 0)
 
     def test_returned_app(self):
-        import tests.fixtureapps.runner as _apps
+        from tests.fixtureapps import runner as _apps
 
         def check_server(app, **kw):
             self.assertIs(app, _apps.app)
@@ -162,7 +162,7 @@ class Test_helper(unittest.TestCase):
                 raise ImportError("My reason")
             except ImportError:
                 self.assertEqual(show_exception(sys.stderr), None)
-            self.assertRegexpMatches(captured.getvalue(), regex)
+            self.assertRegex(captured.getvalue(), regex)
         captured.close()
 
         regex = (
@@ -175,15 +175,15 @@ class Test_helper(unittest.TestCase):
                 raise ImportError
             except ImportError:
                 self.assertEqual(show_exception(sys.stderr), None)
-            self.assertRegexpMatches(captured.getvalue(), regex)
+            self.assertRegex(captured.getvalue(), regex)
         captured.close()
 
 
 @contextlib.contextmanager
 def capture():
-    from waitress.compat import NativeIO
+    from io import StringIO
 
-    fd = NativeIO()
+    fd = StringIO()
     sys.stdout = fd
     sys.stderr = fd
     yield fd
diff --git a/tests/test_server.py b/tests/test_server.py
index 9134fb8..05f6b4e 100644
--- a/tests/test_server.py
+++ b/tests/test_server.py
@@ -240,7 +240,7 @@ class TestWSGIServer(unittest.TestCase):
         inst.adj = DummyAdj
 
         def foo():
-            raise socket.error
+            raise OSError
 
         inst.accept = foo
         inst.logger = DummyLogger()
@@ -263,7 +263,7 @@ class TestWSGIServer(unittest.TestCase):
     def test_maintenance(self):
         inst = self._makeOneWithMap()
 
-        class DummyChannel(object):
+        class DummyChannel:
             requests = []
 
         zombie = DummyChannel()
@@ -274,8 +274,8 @@ class TestWSGIServer(unittest.TestCase):
         self.assertEqual(zombie.will_close, True)
 
     def test_backward_compatibility(self):
-        from waitress.server import WSGIServer, TcpWSGIServer
         from waitress.adjustments import Adjustments
+        from waitress.server import TcpWSGIServer, WSGIServer
 
         self.assertTrue(WSGIServer is TcpWSGIServer)
         self.inst = WSGIServer(None, _start=False, port=1234)
@@ -411,8 +411,8 @@ if hasattr(socket, "AF_UNIX"):
 
         def test_create_with_unix_socket(self):
             from waitress.server import (
-                MultiSocketServer,
                 BaseWSGIServer,
+                MultiSocketServer,
                 TcpWSGIServer,
                 UnixWSGIServer,
             )
@@ -479,7 +479,7 @@ class DummySock(socket.socket):
         pass
 
 
-class DummyTaskDispatcher(object):
+class DummyTaskDispatcher:
     def __init__(self):
         self.tasks = []
 
@@ -490,7 +490,7 @@ class DummyTaskDispatcher(object):
         self.was_shutdown = True
 
 
-class DummyTask(object):
+class DummyTask:
     serviced = False
     start_response_called = False
     wrote_header = False
@@ -512,12 +512,12 @@ class DummyAdj:
     channel_timeout = 300
 
 
-class DummyAsyncore(object):
+class DummyAsyncore:
     def loop(self, timeout=30.0, use_poll=False, map=None, count=None):
         raise SystemExit
 
 
-class DummyTrigger(object):
+class DummyTrigger:
     def pull_trigger(self):
         self.pulled = True
 
@@ -525,7 +525,7 @@ class DummyTrigger(object):
         pass
 
 
-class DummyLogger(object):
+class DummyLogger:
     def __init__(self):
         self.logged = []
 
diff --git a/tests/test_task.py b/tests/test_task.py
index 6466823..0965bf5 100644
--- a/tests/test_task.py
+++ b/tests/test_task.py
@@ -1,5 +1,5 @@
-import unittest
 import io
+import unittest
 
 
 class TestThreadedTaskDispatcher(unittest.TestCase):
@@ -15,7 +15,7 @@ class TestThreadedTaskDispatcher(unittest.TestCase):
 
         class BadDummyTask(DummyTask):
             def service(self):
-                super(BadDummyTask, self).service()
+                super().service()
                 inst.stop_count += 1
                 raise Exception
 
@@ -400,7 +400,7 @@ class TestWSGITask(unittest.TestCase):
         inst = self._makeOne()
 
         def execute():
-            raise socket.error
+            raise OSError
 
         inst.execute = execute
         self.assertRaises(socket.error, inst.service)
@@ -922,7 +922,7 @@ class TestErrorTask(unittest.TestCase):
         self.assertEqual(lines[8], b"(generated by waitress)")
 
 
-class DummyTask(object):
+class DummyTask:
     serviced = False
     cancelled = False
 
@@ -933,7 +933,7 @@ class DummyTask(object):
         self.cancelled = True
 
 
-class DummyAdj(object):
+class DummyAdj:
     log_socket_errors = True
     ident = "waitress"
     host = "127.0.0.1"
@@ -941,7 +941,7 @@ class DummyAdj(object):
     url_prefix = ""
 
 
-class DummyServer(object):
+class DummyServer:
     server_name = "localhost"
     effective_port = 80
 
@@ -949,7 +949,7 @@ class DummyServer(object):
         self.adj = DummyAdj()
 
 
-class DummyChannel(object):
+class DummyChannel:
     closed_when_done = False
     adj = DummyAdj()
     creation_time = 0
@@ -970,7 +970,7 @@ class DummyChannel(object):
         return len(data)
 
 
-class DummyParser(object):
+class DummyParser:
     version = "1.0"
     command = "GET"
     path = "/"
@@ -990,7 +990,7 @@ def filter_lines(s):
     return list(filter(None, s.split(b"\r\n")))
 
 
-class DummyLogger(object):
+class DummyLogger:
     def __init__(self):
         self.logged = []
 
diff --git a/tests/test_trigger.py b/tests/test_trigger.py
index af740f6..265679a 100644
--- a/tests/test_trigger.py
+++ b/tests/test_trigger.py
@@ -1,6 +1,6 @@
-import unittest
 import os
 import sys
+import unittest
 
 if not sys.platform.startswith("win"):
 
diff --git a/tests/test_utilities.py b/tests/test_utilities.py
index 15cd24f..ea08477 100644
--- a/tests/test_utilities.py
+++ b/tests/test_utilities.py
@@ -39,16 +39,17 @@ class Test_parse_http_date(unittest.TestCase):
 
 class Test_build_http_date(unittest.TestCase):
     def test_rountdrip(self):
-        from waitress.utilities import build_http_date, parse_http_date
         from time import time
 
+        from waitress.utilities import build_http_date, parse_http_date
+
         t = int(time())
         self.assertEqual(t, parse_http_date(build_http_date(t)))
 
 
 class Test_unpack_rfc850(unittest.TestCase):
     def _callFUT(self, val):
-        from waitress.utilities import unpack_rfc850, rfc850_reg
+        from waitress.utilities import rfc850_reg, unpack_rfc850
 
         return unpack_rfc850(rfc850_reg.match(val.lower()))
 
@@ -60,7 +61,7 @@ class Test_unpack_rfc850(unittest.TestCase):
 
 class Test_unpack_rfc_822(unittest.TestCase):
     def _callFUT(self, val):
-        from waitress.utilities import unpack_rfc822, rfc822_reg
+        from waitress.utilities import rfc822_reg, unpack_rfc822
 
         return unpack_rfc822(rfc822_reg.match(val.lower()))
 
diff --git a/tests/test_wasyncore.py b/tests/test_wasyncore.py
index 9c23509..970e993 100644
--- a/tests/test_wasyncore.py
+++ b/tests/test_wasyncore.py
@@ -1,21 +1,21 @@
-from waitress import wasyncore as asyncore
-from waitress import compat
+import _thread as thread
 import contextlib
+import errno
 import functools
 import gc
-import unittest
-import select
+from io import BytesIO
 import os
-import socket
-import sys
-import time
-import errno
 import re
+import select
+import socket
 import struct
+import sys
 import threading
+import time
+import unittest
 import warnings
 
-from io import BytesIO
+from waitress import compat, wasyncore as asyncore
 
 TIMEOUT = 3
 HAS_UNIX_SOCKETS = hasattr(socket, "AF_UNIX")
@@ -24,6 +24,7 @@ HOSTv4 = "127.0.0.1"
 HOSTv6 = "::1"
 
 # Filename used for testing
+
 if os.name == "java":  # pragma: no cover
     # Jython disallows @ in module names
     TESTFN = "$test"
@@ -33,7 +34,7 @@ else:
 TESTFN = "{}_{}_tmp".format(TESTFN, os.getpid())
 
 
-class DummyLogger(object):  # pragma: no cover
+class DummyLogger:  # pragma: no cover
     def __init__(self):
         self.messages = []
 
@@ -41,7 +42,7 @@ class DummyLogger(object):  # pragma: no cover
         self.messages.append((severity, message))
 
 
-class WarningsRecorder(object):  # pragma: no cover
+class WarningsRecorder:  # pragma: no cover
     """Convenience wrapper for the warnings list returned on
        entry to the warnings.catch_warnings() context manager.
     """
@@ -67,6 +68,7 @@ def _filterwarnings(filters, quiet=False):  # pragma: no cover
     # in order to re-raise the warnings.
     frame = sys._getframe(2)
     registry = frame.f_globals.get("__warningregistry__")
+
     if registry:
         registry.clear()
     with warnings.catch_warnings(record=True) as w:
@@ -78,19 +80,25 @@ def _filterwarnings(filters, quiet=False):  # pragma: no cover
     # Filter the recorded warnings
     reraise = list(w)
     missing = []
+
     for msg, cat in filters:
         seen = False
+
         for w in reraise[:]:
             warning = w.message
             # Filter out the matching messages
+
             if re.match(msg, str(warning), re.I) and issubclass(warning.__class__, cat):
                 seen = True
                 reraise.remove(w)
+
         if not seen and not quiet:
             # This filter caught nothing
             missing.append((msg, cat.__name__))
+
     if reraise:
         raise AssertionError("unhandled warning %s" % reraise[0])
+
     if missing:
         raise AssertionError("filter (%r, %s) did not catch any warning" % missing[0])
 
@@ -111,11 +119,14 @@ def check_warnings(*filters, **kwargs):  # pragma: no cover
         check_warnings(("", Warning), quiet=True)
     """
     quiet = kwargs.get("quiet")
+
     if not filters:
         filters = (("", Warning),)
         # Preserve backward compatibility
+
         if quiet is None:
             quiet = True
+
     return _filterwarnings(filters, quiet)
 
 
@@ -130,6 +141,7 @@ def gc_collect():  # pragma: no cover
     objects to disappear.
     """
     gc.collect()
+
     if sys.platform.startswith("java"):
         time.sleep(0.1)
     gc.collect()
@@ -137,7 +149,7 @@ def gc_collect():  # pragma: no cover
 
 
 def threading_setup():  # pragma: no cover
-    return (compat.thread._count(), None)
+    return (thread._count(), None)
 
 
 def threading_cleanup(*original_values):  # pragma: no cover
@@ -146,7 +158,8 @@ def threading_cleanup(*original_values):  # pragma: no cover
     _MAX_COUNT = 100
 
     for count in range(_MAX_COUNT):
-        values = (compat.thread._count(), None)
+        values = (thread._count(), None)
+
         if values == original_values:
             break
 
@@ -186,6 +199,7 @@ def join_thread(thread, timeout=30.0):  # pragma: no cover
     after timeout seconds.
     """
     thread.join(timeout)
+
     if thread.is_alive():
         msg = "failed to join the thread in %.1f seconds" % timeout
         raise AssertionError(msg)
@@ -213,6 +227,7 @@ def bind_port(sock, host=HOST):  # pragma: no cover
                     "tests should never set the SO_REUSEADDR "
                     "socket option on TCP/IP sockets!"
                 )
+
         if hasattr(socket, "SO_REUSEPORT"):
             try:
                 if sock.getsockopt(socket.SOL_SOCKET, socket.SO_REUSEPORT) == 1:
@@ -225,11 +240,13 @@ def bind_port(sock, host=HOST):  # pragma: no cover
                 # thus defining SO_REUSEPORT but this process is running
                 # under an older kernel that does not support SO_REUSEPORT.
                 pass
+
         if hasattr(socket, "SO_EXCLUSIVEADDRUSE"):
             sock.setsockopt(socket.SOL_SOCKET, socket.SO_EXCLUSIVEADDRUSE, 1)
 
     sock.bind((host, 0))
     port = sock.getsockname()[1]
+
     return port
 
 
@@ -303,13 +320,16 @@ def capture_server(evt, buf, serv):  # pragma no cover
     else:
         n = 200
         start = time.time()
+
         while n > 0 and time.time() - start < 3.0:
             r, w, e = select.select([conn], [], [], 0.1)
+
             if r:
                 n -= 1
                 data = conn.recv(10)
                 # keep everything except for the newline terminator
                 buf.write(data.replace(b"\n", b""))
+
                 if b"\n" in data:
                     break
             time.sleep(0.01)
@@ -332,6 +352,7 @@ def bind_unix_socket(sock, addr):  # pragma: no cover
 
 def bind_af_aware(sock, addr):
     """Helper function to bind a socket according to its family."""
+
     if HAS_UNIX_SOCKETS and sock.family == socket.AF_UNIX:
         # Make sure the path doesn't exist.
         unlink(addr)
@@ -346,6 +367,7 @@ if sys.platform.startswith("win"):  # pragma: no cover
         # Perform the operation
         func(pathname)
         # Now setup the wait loop
+
         if waitall:
             dirname = pathname
         else:
@@ -358,6 +380,7 @@ if sys.platform.startswith("win"):  # pragma: no cover
         # Testing on an i7@4.3GHz shows that usually only 1 iteration is
         # required when contention occurs.
         timeout = 0.001
+
         while timeout < 1.0:
             # Note we are only testing for the existence of the file(s) in
             # the contents of the directory regardless of any security or
@@ -367,6 +390,7 @@ if sys.platform.startswith("win"):  # pragma: no cover
             # Other Windows APIs can fail or give incorrect results when
             # dealing with files that are pending deletion.
             L = os.listdir(dirname)
+
             if not (L if waitall else name in L):
                 return
             # Increase the timeout and try again
@@ -395,17 +419,20 @@ def unlink(filename):
 
 def _is_ipv6_enabled():  # pragma: no cover
     """Check whether IPv6 is enabled on this host."""
+
     if compat.HAS_IPV6:
         sock = None
         try:
             sock = socket.socket(socket.AF_INET6, socket.SOCK_STREAM)
             sock.bind(("::1", 0))
+
             return True
-        except socket.error:
+        except OSError:
             pass
         finally:
             if sock:
                 sock.close()
+
     return False
 
 
@@ -487,6 +514,7 @@ class HelperFunctionTests(unittest.TestCase):
 
             # Only the attribute modified by the routine we expect to be
             # called should be True.
+
             for attr in attributes:
                 self.assertEqual(getattr(tobj, attr), attr == expectedattr)
 
@@ -513,6 +541,7 @@ class HelperFunctionTests(unittest.TestCase):
 
         l = []
         testmap = {}
+
         for i in range(10):
             c = dummychannel()
             l.append(c)
@@ -606,6 +635,7 @@ class DispatcherTests(unittest.TestCase):
     def test_strerror(self):
         # refers to bug #8573
         err = asyncore._strerror(errno.EPERM)
+
         if hasattr(os, "strerror"):
             self.assertEqual(err, os.strerror(errno.EPERM))
         err = asyncore._strerror(-1)
@@ -656,6 +686,7 @@ class DispatcherWithSendTests(unittest.TestCase):
             d.send(b"\n")
 
             n = 1000
+
             while d.out_buffer and n > 0:  # pragma: no cover
                 asyncore.poll()
                 n -= 1
@@ -723,6 +754,7 @@ class FileWrapperTest(unittest.TestCase):
     def test_resource_warning(self):
         # Issue #11453
         got_warning = False
+
         while got_warning is False:
             # we try until we get the outcome we want because this
             # test is not deterministic (gc_collect() may not
@@ -732,7 +764,7 @@ class FileWrapperTest(unittest.TestCase):
             os.close(fd)
 
             try:
-                with check_warnings(("", compat.ResourceWarning)):
+                with check_warnings(("", ResourceWarning)):
                     f = None
                     gc_collect()
             except AssertionError:  # pragma: no cover
@@ -819,8 +851,10 @@ class BaseTestAPI:
     def loop_waiting_for_flag(self, instance, timeout=5):  # pragma: no cover
         timeout = float(timeout) / 100
         count = 100
+
         while asyncore.socket_map and count > 0:
             asyncore.loop(timeout=0.01, count=1, use_poll=self.use_poll)
+
             if instance.flag:
                 return
             count -= 1
@@ -966,6 +1000,7 @@ class BaseTestAPI:
         # Make sure handle_expt is called on OOB data received.
         # Note: this might fail on some platforms as OOB data is
         # tenuously supported and rarely used.
+
         if HAS_UNIX_SOCKETS and self.family == socket.AF_UNIX:
             self.skipTest("Not applicable to AF_UNIX sockets.")
 
@@ -980,7 +1015,7 @@ class BaseTestAPI:
         class TestHandler(BaseTestHandler):
             def __init__(self, conn):
                 BaseTestHandler.__init__(self, conn)
-                self.socket.send(compat.tobytes(chr(244)), socket.MSG_OOB)
+                self.socket.send(chr(244).encode("latin-1"), socket.MSG_OOB)
 
         server = BaseServer(self.family, self.addr, TestHandler)
         client = TestClient(self.family, server.address)
@@ -1082,6 +1117,7 @@ class BaseTestAPI:
     @reap_threads
     def test_quick_connect(self):  # pragma: no cover
         # see: http://bugs.python.org/issue10340
+
         if self.family not in (socket.AF_INET, getattr(socket, "AF_INET6", object())):
             self.skipTest("test specific to AF_INET and AF_INET6")
 
@@ -1420,7 +1456,7 @@ class Test_dispatcher(unittest.TestCase):
         sock = dummysocket()
 
         def getpeername():
-            raise socket.error(errno.EBADF)
+            raise OSError(errno.EBADF)
 
         map = {}
         sock.getpeername = getpeername
@@ -1454,7 +1490,7 @@ class Test_dispatcher(unittest.TestCase):
 
         def setsockopt(*arg, **kw):
             sock.errored = True
-            raise socket.error
+            raise OSError
 
         sock.setsockopt = setsockopt
         sock.getsockopt = lambda *arg: 0
@@ -1486,7 +1522,7 @@ class Test_dispatcher(unittest.TestCase):
         map = {}
 
         def accept(*arg, **kw):
-            raise socket.error(122)
+            raise OSError(122)
 
         sock.accept = accept
         inst = self._makeOne(sock=sock, map=map)
@@ -1497,7 +1533,7 @@ class Test_dispatcher(unittest.TestCase):
         map = {}
 
         def send(*arg, **kw):
-            raise socket.error(errno.EWOULDBLOCK)
+            raise OSError(errno.EWOULDBLOCK)
 
         sock.send = send
         inst = self._makeOne(sock=sock, map=map)
@@ -1509,7 +1545,7 @@ class Test_dispatcher(unittest.TestCase):
         map = {}
 
         def send(*arg, **kw):
-            raise socket.error(122)
+            raise OSError(122)
 
         sock.send = send
         inst = self._makeOne(sock=sock, map=map)
@@ -1520,7 +1556,7 @@ class Test_dispatcher(unittest.TestCase):
         map = {}
 
         def recv(*arg, **kw):
-            raise socket.error(errno.ECONNRESET)
+            raise OSError(errno.ECONNRESET)
 
         def handle_close():
             inst.close_handled = True
@@ -1537,7 +1573,7 @@ class Test_dispatcher(unittest.TestCase):
         map = {}
 
         def close():
-            raise socket.error(122)
+            raise OSError(122)
 
         sock.close = close
         inst = self._makeOne(sock=sock, map=map)
@@ -1680,7 +1716,7 @@ class Test_close_all(unittest.TestCase):
         self.assertRaises(RuntimeError, self._callFUT, map)
 
 
-class DummyDispatcher(object):
+class DummyDispatcher:
     read_event_handled = False
     write_event_handled = False
     expt_event_handled = False
@@ -1693,16 +1729,19 @@ class DummyDispatcher(object):
 
     def handle_read_event(self):
         self.read_event_handled = True
+
         if self.exc is not None:
             raise self.exc
 
     def handle_write_event(self):
         self.write_event_handled = True
+
         if self.exc is not None:
             raise self.exc
 
     def handle_expt_event(self):
         self.expt_event_handled = True
+
         if self.exc is not None:
             raise self.exc
 
@@ -1723,7 +1762,7 @@ class DummyDispatcher(object):
             raise self.exc
 
 
-class DummyTime(object):
+class DummyTime:
     def __init__(self):
         self.sleepvals = []
 
@@ -1731,7 +1770,7 @@ class DummyTime(object):
         self.sleepvals.append(val)
 
 
-class DummySelect(object):
+class DummySelect:
     error = select.error
 
     def __init__(self, exc=None, pollster=None):
@@ -1741,6 +1780,7 @@ class DummySelect(object):
 
     def select(self, *arg):
         self.selected.append(arg)
+
         if self.exc is not None:
             raise self.exc
 
@@ -1748,13 +1788,14 @@ class DummySelect(object):
         return self.pollster
 
 
-class DummyPollster(object):
+class DummyPollster:
     def __init__(self, exc=None):
         self.polled = []
         self.exc = exc
 
     def poll(self, timeout):
         self.polled.append(timeout)
+
         if self.exc is not None:
             raise self.exc
         else:  # pragma: no cover
diff --git a/tox.ini b/tox.ini
index 6ca71ad..ff0ff14 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,8 +1,8 @@
 [tox]
 envlist =
     lint,
-    py27,pypy,
     py35,py36,py37,py38,pypy3,
+    py39,
     docs,
     coverage
 isolated_build = True
@@ -26,12 +26,13 @@ deps =
     coverage
 setenv =
     COVERAGE_FILE=.coverage
-depends = py27, py38
+depends = py38
 
 [testenv:lint]
 skip_install = True
 commands =
     black --check --diff .
+    isort --check-only --df src/waitress tests
     check-manifest
     # flake8 src/waitress/ tests
     # build sdist/wheel
@@ -39,12 +40,13 @@ commands =
     twine check dist/*
 deps =
     black
-    readme_renderer
     check-manifest
-    pep517
-    twine
     flake8
     flake8-bugbear
+    isort
+    pep517
+    readme_renderer
+    twine
 
 [testenv:docs]
 whitelist_externals =
@@ -62,12 +64,14 @@ deps =
     flake8
     flake8-bugbear
 
-[testenv:run-black]
+[testenv:run-format]
 skip_install = True
 commands =
+    isort src/waitress tests
     black .
 deps =
     black
+    isort
 
 [testenv:build]
 skip_install = true