Drop support for Python 2.7, 3.5, 3.6. (#266)

Co-authored-by: Jens Vagelpohl <jens@plyp.com>

13 files changed, 50 insertions, 213 deletions

diff --git a/src/zope/interface/common/__init__.py b/src/zope/interface/common/__init__.py
index 137e938..56f4566 100644
--- a/src/zope/interface/common/__init__.py
+++ b/src/zope/interface/common/__init__.py
@@ -28,7 +28,7 @@ __all__ = [
 # pylint:disable=no-self-argument,no-method-argument
 # pylint:disable=unexpected-special-method-signature
 
-class optional(object):
+class optional:
     # Apply this decorator to a method definition to make it
     # optional (remove it from the list of required names), overriding
     # the definition inherited from the ABC.
@@ -162,7 +162,7 @@ class ABCInterfaceClass(InterfaceClass):
             return ''
 
         docs = "\n\nThe following methods are optional:\n - " + "\n-".join(
-            "%s\n%s" % (k, v.__doc__) for k, v in optionals.items()
+            "{}\n{}".format(k, v.__doc__) for k, v in optionals.items()
         )
         return docs
 
@@ -175,7 +175,7 @@ class ABCInterfaceClass(InterfaceClass):
                 return "`%s`" % name
             if mod == '_io':
                 mod = 'io'
-            return "`%s.%s`" % (mod, name)
+            return "`{}.{}`".format(mod, name)
         implementations_doc = "\n - ".join(
             ref(c)
             for c in sorted(self.getRegisteredConformers(), key=ref)
@@ -187,7 +187,7 @@ class ABCInterfaceClass(InterfaceClass):
         based_on_doc = based_on_doc.splitlines()
         based_on_doc = based_on_doc[0] if based_on_doc else ''
 
-        doc = """Interface for the ABC `%s.%s`.\n\n%s%s%s""" % (
+        doc = """Interface for the ABC `{}.{}`.\n\n{}{}{}""".format(
             based_on.__module__, based_on.__name__,
             attrs.get('__doc__', based_on_doc),
             self.__optional_methods_to_docs(attrs),
diff --git a/src/zope/interface/common/builtins.py b/src/zope/interface/common/builtins.py
index a07c0a3..17090e4 100644
--- a/src/zope/interface/common/builtins.py
+++ b/src/zope/interface/common/builtins.py
@@ -17,7 +17,6 @@ that they implement the appropriate interface.
 
 .. versionadded:: 5.0.0
 """
-from __future__ import absolute_import
 
 from zope.interface import classImplements
 
@@ -60,12 +59,11 @@ class ITuple(collections.ISequence):
 
 class ITextString(collections.ISequence):
     """
-    Interface for text (unicode) strings.
+    Interface for text ("unicode") strings.
 
-    On Python 2, this is :class:`unicode`. On Python 3,
-    this is :class:`str`
+    This is :class:`str`
     """
-    extra_classes = (type(u'unicode'),)
+    extra_classes = (str,)
 
 
 class IByteString(collections.IByteString):
@@ -81,12 +79,11 @@ class IByteString(collections.IByteString):
     extra_classes = (bytes,)
 
 
-class INativeString(IByteString if str is bytes else ITextString):
+class INativeString(ITextString):
     """
     Interface for native strings.
 
-    On all Python versions, this is :class:`str`. On Python 2,
-    this extends :class:`IByteString`, while on Python 3 it extends
+    On all Python versions, this is :class:`str`. Tt extends
     :class:`ITextString`.
     """
 # We're not extending ABCInterface so extra_classes won't work
@@ -119,7 +116,4 @@ class IFile(io.IIOBase):
     many different classes that implement different interfaces from
     :mod:`zope.interface.common.io`.
     """
-    try:
-        extra_classes = (file,)
-    except NameError:
-        extra_classes = ()
+    extra_classes = ()
diff --git a/src/zope/interface/common/collections.py b/src/zope/interface/common/collections.py
index 00e2b8c..c549028 100644
--- a/src/zope/interface/common/collections.py
+++ b/src/zope/interface/common/collections.py
@@ -29,37 +29,16 @@ is, ``verifyObject(ISequence, list()))`` will pass, for example), a few might no
 
 .. versionadded:: 5.0.0
 """
-from __future__ import absolute_import
 
 import sys
 
 from abc import ABCMeta
-# The collections imports are here, and not in
-# zope.interface._compat to avoid importing collections
-# unless requested. It's a big import.
-try:
-    from collections import abc
-except ImportError:
-    import collections as abc
+from collections import abc
 from collections import OrderedDict
-try:
-    # On Python 3, all of these extend the appropriate collection ABC,
-    # but on Python 2, UserDict does not (though it is registered as a
-    # MutableMapping). (Importantly, UserDict on Python 2 is *not*
-    # registered, because it's not iterable.) Extending the ABC is not
-    # taken into account for interface declarations, though, so we
-    # need to be explicit about it.
-    from collections import UserList
-    from collections import UserDict
-    from collections import UserString
-except ImportError:
-    # Python 2
-    from UserList import UserList
-    from UserDict import IterableUserDict as UserDict
-    from UserString import UserString
-
-from zope.interface._compat import PYTHON2 as PY2
-from zope.interface._compat import PYTHON3 as PY3
+from collections import UserList
+from collections import UserDict
+from collections import UserString
+
 from zope.interface.common import ABCInterface
 from zope.interface.common import optional
 
@@ -68,8 +47,6 @@ from zope.interface.common import optional
 # pylint:disable=unexpected-special-method-signature
 # pylint:disable=no-value-for-parameter
 
-PY35 = sys.version_info[:2] >= (3, 5)
-PY36 = sys.version_info[:2] >= (3, 6)
 
 def _new_in_ver(name, ver,
                 bases_if_missing=(ABCMeta,),
@@ -144,7 +121,7 @@ class IIterator(IIterable):
     abc = abc.Iterator
 
 class IReversible(IIterable):
-    abc = _new_in_ver('Reversible', PY36, (IIterable.getABC(),))
+    abc = _new_in_ver('Reversible', True, (IIterable.getABC(),))
 
     @optional
     def __reversed__():
@@ -155,8 +132,8 @@ class IReversible(IIterable):
         """
 
 class IGenerator(IIterator):
-    # New in 3.5
-    abc = _new_in_ver('Generator', PY35, (IIterator.getABC(),))
+    # New in Python 3.5
+    abc = _new_in_ver('Generator', True, (IIterator.getABC(),))
 
 
 class ISized(ABCInterface):
@@ -168,7 +145,7 @@ class ISized(ABCInterface):
 class ICollection(ISized,
                   IIterable,
                   IContainer):
-    abc = _new_in_ver('Collection', PY36,
+    abc = _new_in_ver('Collection', True,
                       (ISized.getABC(), IIterable.getABC(), IContainer.getABC()))
 
 
@@ -205,7 +182,7 @@ class IByteString(ISequence):
     """
     This unifies `bytes` and `bytearray`.
     """
-    abc = _new_in_ver('ByteString', PY3,
+    abc = _new_in_ver('ByteString', True,
                       (ISequence.getABC(),),
                       (bytes, bytearray))
 
@@ -226,14 +203,6 @@ class IMapping(ICollection):
     # produces an inconsistent IRO if we also try to register it
     # here.
     ignored_classes = (OrderedDict,)
-    if PY2:
-        @optional
-        def __eq__(other):
-            """
-            The interpreter will supply one.
-            """
-
-        __ne__ = __eq__
 
 
 class IMutableMapping(IMapping):
@@ -265,20 +234,20 @@ class IValuesView(IMappingView, ICollection):
         """
 
 class IAwaitable(ABCInterface):
-    abc = _new_in_ver('Awaitable', PY35)
+    abc = _new_in_ver('Awaitable', True)
 
 
 class ICoroutine(IAwaitable):
-    abc = _new_in_ver('Coroutine', PY35)
+    abc = _new_in_ver('Coroutine', True)
 
 
 class IAsyncIterable(ABCInterface):
-    abc = _new_in_ver('AsyncIterable', PY35)
+    abc = _new_in_ver('AsyncIterable', True)
 
 
 class IAsyncIterator(IAsyncIterable):
-    abc = _new_in_ver('AsyncIterator', PY35)
+    abc = _new_in_ver('AsyncIterator', True)
 
 
 class IAsyncGenerator(IAsyncIterator):
-    abc = _new_in_ver('AsyncGenerator', PY36)
+    abc = _new_in_ver('AsyncGenerator', True)
diff --git a/src/zope/interface/common/interfaces.py b/src/zope/interface/common/interfaces.py
index 4308e0a..70bd294 100644
--- a/src/zope/interface/common/interfaces.py
+++ b/src/zope/interface/common/interfaces.py
@@ -22,11 +22,7 @@ classImplements(Exception, IException)
 
 
 class IStandardError(IException):
-    "Interface for `StandardError` (Python 2 only.)"
-try:
-    classImplements(StandardError, IStandardError)
-except NameError:  #pragma NO COVER
-    pass # StandardError does not exist in Python 3
+    "Interface for `StandardError` (no longer existing.)"
 
 
 class IWarning(IException):
diff --git a/src/zope/interface/common/io.py b/src/zope/interface/common/io.py
index 540d53a..0d6f3ba 100644
--- a/src/zope/interface/common/io.py
+++ b/src/zope/interface/common/io.py
@@ -18,7 +18,6 @@ that they implement the appropriate interface.
 
 .. versionadded:: 5.0.0
 """
-from __future__ import absolute_import
 
 import io as abc
 
@@ -37,16 +36,7 @@ class IRawIOBase(IIOBase):
 
 class IBufferedIOBase(IIOBase):
     abc = abc.BufferedIOBase
-    try:
-        import cStringIO
-    except ImportError:
-        # Python 3
-        extra_classes = ()
-    else:
-        import StringIO
-        extra_classes = (StringIO.StringIO, cStringIO.InputType, cStringIO.OutputType)
-        del cStringIO
-        del StringIO
+    extra_classes = ()
 
 
 class ITextIOBase(IIOBase):
diff --git a/src/zope/interface/common/mapping.py b/src/zope/interface/common/mapping.py
index de56cf8..d043333 100644
--- a/src/zope/interface/common/mapping.py
+++ b/src/zope/interface/common/mapping.py
@@ -29,7 +29,6 @@ implement ``IMutableMapping``, but *do not* implement any of the
 interfaces in this module.
 """
 from zope.interface import Interface
-from zope.interface._compat import PYTHON2 as PY2
 from zope.interface.common import collections
 
 class IItemMapping(Interface):
@@ -103,20 +102,8 @@ class IIterableMapping(IEnumerableMapping):
     """A mapping that has distinct methods for iterating
     without copying.
 
-    On Python 2, a `dict` has these methods, but on Python 3
-    the methods defined in `IEnumerableMapping` already iterate
-    without copying.
     """
 
-    if PY2:
-        def iterkeys():
-            "iterate over keys; equivalent to ``__iter__``"
-
-        def itervalues():
-            "iterate over values"
-
-        def iteritems():
-            "iterate over items"
 
 class IClonableMapping(Interface):
     """Something that can produce a copy of itself.
@@ -131,13 +118,10 @@ class IExtendedReadMapping(IIterableMapping):
     """
     Something with a particular method equivalent to ``__contains__``.
 
-    On Python 2, `dict` provides this method, but it was removed
+    On Python 2, `dict` provided the ``has_key`` method, but it was removed
     in Python 3.
     """
 
-    if PY2:
-        def has_key(key):
-            """Tell if a key exists in the mapping; equivalent to ``__contains__``"""
 
 class IExtendedWriteMapping(IWriteMapping):
     """Additional mutation methods.
diff --git a/src/zope/interface/common/numbers.py b/src/zope/interface/common/numbers.py
index 3bf9206..6b20e09 100644
--- a/src/zope/interface/common/numbers.py
+++ b/src/zope/interface/common/numbers.py
@@ -18,14 +18,12 @@ that they implement the appropriate interface.
 
 .. versionadded:: 5.0.0
 """
-from __future__ import absolute_import
 
 import numbers as abc
 
 from zope.interface.common import ABCInterface
 from zope.interface.common import optional
 
-from zope.interface._compat import PYTHON2 as PY2
 
 # pylint:disable=inherit-non-class,
 # pylint:disable=no-self-argument,no-method-argument
@@ -46,14 +44,6 @@ class IComplex(INumber):
         Rarely implemented, even in builtin types.
         """
 
-    if PY2:
-        @optional
-        def __eq__(other):
-            """
-            The interpreter may supply one through complicated rules.
-            """
-
-        __ne__ = __eq__
 
 class IReal(IComplex):
     abc = abc.Real
@@ -66,15 +56,6 @@ class IReal(IComplex):
 
     __floor__ = __ceil__ = __complex__
 
-    if PY2:
-        @optional
-        def __le__(other):
-            """
-            The interpreter may supply one through complicated rules.
-            """
-
-        __lt__ = __le__
-
 
 class IRational(IReal):
     abc = abc.Rational
diff --git a/src/zope/interface/common/sequence.py b/src/zope/interface/common/sequence.py
index da4bc84..5edc73d 100644
--- a/src/zope/interface/common/sequence.py
+++ b/src/zope/interface/common/sequence.py
@@ -32,7 +32,6 @@ in this module.
 __docformat__ = 'restructuredtext'
 from zope.interface import Interface
 from zope.interface.common import collections
-from zope.interface._compat import PYTHON2 as PY2
 
 class IMinimalSequence(collections.IIterable):
     """Most basic sequence interface.
@@ -107,14 +106,6 @@ class IReadSequence(collections.IContainer, IFiniteSequence):
     def __rmul__(n):
         """``x.__rmul__(n) <==> n * x``"""
 
-    if PY2:
-        def __getslice__(i, j):
-            """``x.__getslice__(i, j) <==> x[i:j]``
-
-            Use of negative indices is not supported.
-
-            Deprecated since Python 2.0 but still a part of `UserList`.
-            """
 
 class IExtendedReadSequence(IReadSequence):
     """Full read interface for lists"""
@@ -145,23 +136,6 @@ class IUniqueMemberWriteSequence(Interface):
         supports slice objects.
         """
 
-    if PY2:
-        def __setslice__(i, j, other):
-            """``x.__setslice__(i, j, other) <==> x[i:j] = other``
-
-            Use of negative indices is not supported.
-
-            Deprecated since Python 2.0 but still a part of `UserList`.
-            """
-
-        def __delslice__(i, j):
-            """``x.__delslice__(i, j) <==> del x[i:j]``
-
-            Use of negative indices is not supported.
-
-            Deprecated since Python 2.0 but still a part of `UserList`.
-            """
-
     def __iadd__(y):
         """``x.__iadd__(y) <==> x += y``"""
 
diff --git a/src/zope/interface/common/tests/__init__.py b/src/zope/interface/common/tests/__init__.py
index 2023072..0503495 100644
--- a/src/zope/interface/common/tests/__init__.py
+++ b/src/zope/interface/common/tests/__init__.py
@@ -60,7 +60,7 @@ def add_verify_tests(cls, iface_classes_iter):
 
                 self.assertTrue(self.verify(iface, stdlib_class))
 
-            suffix = "%s_%s_%s_%s" % (
+            suffix = "{}_{}_{}_{}".format(
                 stdlib_class.__module__.replace('.', '_'),
                 stdlib_class.__name__,
                 iface.__module__.replace('.', '_'),
diff --git a/src/zope/interface/common/tests/basemapping.py b/src/zope/interface/common/tests/basemapping.py
index b756dca..6fe91a1 100644
--- a/src/zope/interface/common/tests/basemapping.py
+++ b/src/zope/interface/common/tests/basemapping.py
@@ -63,7 +63,7 @@ def testIEnumerableMapping(self, inst, state):
     test___len__(self, inst, state)
 
 
-class BaseTestIReadMapping(object):
+class BaseTestIReadMapping:
     def testIReadMapping(self):
         inst = self._IReadMapping__sample()
         state = self._IReadMapping__stateDict()
diff --git a/src/zope/interface/common/tests/test_builtins.py b/src/zope/interface/common/tests/test_builtins.py
index 1f0d338..cf7019b 100644
--- a/src/zope/interface/common/tests/test_builtins.py
+++ b/src/zope/interface/common/tests/test_builtins.py
@@ -9,11 +9,9 @@
 # WARRANTIES OF TITLE, MERCHANTABILITY, AGAINST INFRINGEMENT, AND FITNESS
 # FOR A PARTICULAR PURPOSE.
 ##############################################################################
-from __future__ import absolute_import
 
 import unittest
 
-from zope.interface._compat import PYTHON2 as PY2
 from zope.interface.common import builtins
 
 from . import VerifyClassMixin
@@ -29,12 +27,12 @@ class TestVerifyClass(VerifyClassMixin,
 add_verify_tests(TestVerifyClass, (
     (builtins.IList, (list,)),
     (builtins.ITuple, (tuple,)),
-    (builtins.ITextString, (type(u'abc'),)),
+    (builtins.ITextString, (str,)),
     (builtins.IByteString, (bytes,)),
     (builtins.INativeString, (str,)),
     (builtins.IBool, (bool,)),
     (builtins.IDict, (dict,)),
-    (builtins.IFile, (file,) if PY2 else ()),
+    (builtins.IFile, ()),
 ))
 
 
diff --git a/src/zope/interface/common/tests/test_collections.py b/src/zope/interface/common/tests/test_collections.py
index 152626b..2bd6f50 100644
--- a/src/zope/interface/common/tests/test_collections.py
+++ b/src/zope/interface/common/tests/test_collections.py
@@ -13,18 +13,12 @@
 
 import array
 import unittest
-try:
-    import collections.abc as abc
-except ImportError:
-    import collections as abc
+from collections import abc
 from collections import deque
 from collections import OrderedDict
 
 
-try:
-    from types import MappingProxyType
-except ImportError:
-    MappingProxyType = object()
+from types import MappingProxyType
 
 from zope.interface import Invalid
 
@@ -34,7 +28,7 @@ from zope.interface.common import collections
 
 
 from zope.interface._compat import PYPY
-from zope.interface._compat import PYTHON2 as PY2
+
 
 from . import add_abc_interface_tests
 from . import VerifyClassMixin
@@ -65,16 +59,6 @@ class TestVerifyClass(VerifyClassMixin, unittest.TestCase):
         self.assertTrue(self.verify(collections.ISequence,
                                     collections.UserString))
 
-    def test_non_iterable_UserDict(self):
-        try:
-            from UserDict import UserDict as NonIterableUserDict # pylint:disable=import-error
-        except ImportError:
-            # Python 3
-            self.skipTest("No UserDict.NonIterableUserDict on Python 3")
-
-        with self.assertRaises(Invalid):
-            self.verify(collections.IMutableMapping, NonIterableUserDict)
-
     # Now we go through the registry, which should have several things,
     # mostly builtins, but if we've imported other libraries already,
     # it could contain things from outside of there too. We aren't concerned
@@ -110,30 +94,13 @@ class TestVerifyClass(VerifyClassMixin, unittest.TestCase):
             # Likewise for index
             range,
         })
-    if PY2:
-        # pylint:disable=undefined-variable,no-member
-        # There are a lot more types that are fundamentally unverifiable on Python 2.
-        UNVERIFIABLE.update({
-            # Missing several key methods like __getitem__
-            basestring,
-            # Missing __iter__ and __contains__, hard to construct.
-            buffer,
-            # Missing ``__contains__``, ``count`` and ``index``.
-            xrange,
-            # These two are missing Set.isdisjoint()
-            type({}.viewitems()),
-            type({}.viewkeys()),
-        })
-        NON_STRICT_RO = {
-        }
-    else:
-        UNVERIFIABLE_RO = {
-            # ``array.array`` fails the ``test_auto_ro_*`` tests with and
-            # without strict RO but only on Windows (AppVeyor) on Python 3.10.0
-            # (in older versions ``array.array`` does not appear as
-            # ``IMutableSequence``).
-            array.array,
-        }
+    UNVERIFIABLE_RO = {
+        # ``array.array`` fails the ``test_auto_ro_*`` tests with and
+        # without strict RO but only on Windows (AppVeyor) on Python 3.10.0
+        # (in older versions ``array.array`` does not appear as
+        # ``IMutableSequence``).
+        array.array,
+    }
 
 add_abc_interface_tests(TestVerifyClass, collections.ISet.__module__)
 
@@ -154,7 +121,7 @@ class TestVerifyObject(VerifyObjectMixin,
         type(iter({}.keys())): lambda: iter({}.keys()),
         type(iter({}.items())): lambda: iter({}.items()),
         type(iter({}.values())): lambda: iter({}.values()),
-        type((i for i in range(1))): lambda: (i for i in range(3)),
+        type(i for i in range(1)): lambda: (i for i in range(3)),
         type(iter([])): lambda: iter([]),
         type(reversed([])): lambda: reversed([]),
         'longrange_iterator': unittest.SkipTest,
@@ -166,16 +133,10 @@ class TestVerifyObject(VerifyObjectMixin,
         type(iter(tuple())): lambda: iter(tuple()),
     }
 
-    if PY2:
-        # pylint:disable=undefined-variable,no-member
-        CONSTRUCTORS.update({
-            collections.IValuesView: {}.viewvalues,
-        })
-    else:
-        UNVERIFIABLE_RO = {
-            # ``array.array`` fails the ``test_auto_ro_*`` tests with and
-            # without strict RO but only on Windows (AppVeyor) on Python 3.10.0
-            # (in older versions ``array.array`` does not appear as
-            # ``IMutableSequence``).
-            array.array,
-        }
+    UNVERIFIABLE_RO = {
+        # ``array.array`` fails the ``test_auto_ro_*`` tests with and
+        # without strict RO but only on Windows (AppVeyor) on Python 3.10.0
+        # (in older versions ``array.array`` does not appear as
+        # ``IMutableSequence``).
+        array.array,
+    }
diff --git a/src/zope/interface/common/tests/test_io.py b/src/zope/interface/common/tests/test_io.py
index c6ff8bd..0e8e74d 100644
--- a/src/zope/interface/common/tests/test_io.py
+++ b/src/zope/interface/common/tests/test_io.py
@@ -40,13 +40,3 @@ class TestVerifyObject(VerifyObjectMixin,
         abc.FileIO: lambda: abc.FileIO(__file__),
         '_WindowsConsoleIO': unittest.SkipTest,
     }
-
-    try:
-        import cStringIO
-    except ImportError:
-        pass
-    else:
-        CONSTRUCTORS.update({
-            cStringIO.InputType: lambda cStringIO=cStringIO: cStringIO.StringIO('abc'),
-            cStringIO.OutputType: cStringIO.StringIO,
-        })