Configure with meta/config. (#243)

* Add support for Python 3.9.
* Improve coverage.

14 files changed, 387 insertions, 184 deletions

diff --git a/.coveragerc b/.coveragerc
index f098024..7b87f85 100644
--- a/.coveragerc
+++ b/.coveragerc
@@ -1,14 +1,29 @@
+# Generated from:
+# https://github.com/zopefoundation/meta/tree/master/config/c-code
 [run]
-branch = True
 source = zope.interface
 # New in 5.0; required for the GHA coveralls submission.
 relative_files = True
+branch = true
+
+[paths]
+source =
+    src/
+    .tox/*/lib/python*/site-packages/
+    .tox/pypy*/site-packages/
 
 [report]
 show_missing = true
+precision = 2
 exclude_lines =
+    except ImportError:
+    if __name__ == '__main__':
     pragma: no cover
-    class I[A-Z]\w+\((Interface|I[A-Z].*)\):
-    raise NotImplementedError
+    pragma: nocover
     raise AssertionError
-    self\.fail
+    raise NotImplementedError
+    raise unittest.Skip
+    self.fail\(
+
+[html]
+directory = parts/htmlcov
diff --git a/.editorconfig b/.editorconfig
new file mode 100644
index 0000000..27282ae
--- /dev/null
+++ b/.editorconfig
@@ -0,0 +1,39 @@
+# Generated from:
+# https://github.com/zopefoundation/meta/tree/master/config/c-code
+#
+# EditorConfig Configuration file, for more details see:
+# http://EditorConfig.org
+# EditorConfig is a convention description, that could be interpreted
+# by multiple editors to enforce common coding conventions for specific
+# file types
+
+# top-most EditorConfig file:
+# Will ignore other EditorConfig files in Home directory or upper tree level.
+root = true
+
+
+[*]  # For All Files
+# Unix-style newlines with a newline ending every file
+end_of_line = lf
+insert_final_newline = true
+trim_trailing_whitespace = true
+# Set default charset
+charset = utf-8
+# Indent style default
+indent_style = space
+# Max Line Length - a hard line wrap, should be disabled
+max_line_length = off
+
+[*.{py,cfg,ini}]
+# 4 space indentation
+indent_size = 4
+
+[*.{yml,zpt,pt,dtml}]
+# 2 space indentation
+indent_size = 2
+
+[{Makefile,.gitmodules}]
+# Tab indentation (no size specified, but view as 4 spaces)
+indent_style = tab
+indent_size = unset
+tab_width = unset
diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index f0f4177..6ef90c0 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -1,7 +1,9 @@
+# Generated from:
+# https://github.com/zopefoundation/meta/tree/master/config/c-code
 ###
 # Initially copied from
 # https://github.com/actions/starter-workflows/blob/main/ci/python-package.yml
-# And later based on the version I (jamadden) updated at
+# And later based on the version jamadden updated at
 # gevent/gevent, and then at zodb/relstorage and zodb/perfmetrics
 #
 # Original comment follows.
@@ -35,14 +37,14 @@
 name: tests
 
 
-# Triggers the workflow on push or pull request events
-on: [push, pull_request]
-# Limiting to particular branches might be helpful to conserve minutes.
-#on:
-  # push:
-  #   branches: [ $default-branch ]
-  # pull_request:
-  #   branches: [ $default-branch ]
+# Triggers the workflow on push or pull request events and periodically
+on:
+  push:
+  pull_request:
+  schedule:
+    - cron: '0 12 * * 0'  # run once a week on Sunday
+  # Allow to run this workflow manually from the Actions tab
+  workflow_dispatch:
 
 env:
   # Weirdly, this has to be a top-level key, not ``defaults.env``
@@ -72,7 +74,6 @@ env:
   ###
 
 
-
 jobs:
   # Because sharing code/steps is so hard, and because it can be
   # extremely valuable to be able to get binary wheels without
@@ -86,13 +87,21 @@ jobs:
   # This division is time-saving for projects that take awhile to
   # build, but somewhat less of a clear-cut win given how quick this
   # is to compile (at least at this writing).
-  build-zope_interface:
+  build-package:
     # Sigh. Note that the matrix must be kept in sync
     # with `test`, and `docs` must use a subset.
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        python-version: [2.7, pypy-2.7, pypy-3.6, 3.5, 3.6, 3.7, 3.8, 3.9]
+        python-version:
+          - 2.7
+          - 3.5
+          - pypy-2.7
+          - pypy-3.6
+          - 3.6
+          - 3.7
+          - 3.8
+          - 3.9
         os: [ubuntu-20.04, macos-latest]
         exclude:
           - os: macos-latest
@@ -131,7 +140,7 @@ jobs:
       - name: Install Build Dependencies
         run: |
           pip install -U pip
-          pip install -U setuptools wheel twine
+          pip install -U setuptools wheel twine cffi
           pip install -U coveralls coverage
 
       - name: Build zope.interface
@@ -165,11 +174,19 @@ jobs:
           twine upload --skip-existing dist/*
 
   test:
-    needs: build-zope_interface
+    needs: build-package
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        python-version: [2.7, pypy-2.7, pypy-3.6, 3.5, 3.6, 3.7, 3.8, 3.9]
+        python-version:
+          - 2.7
+          - 3.5
+          - pypy-2.7
+          - pypy-3.6
+          - 3.6
+          - 3.7
+          - 3.8
+          - 3.9
         os: [ubuntu-20.04, macos-latest]
         exclude:
           - os: macos-latest
@@ -186,6 +203,12 @@ jobs:
         uses: actions/setup-python@v2
         with:
           python-version: ${{ matrix.python-version }}
+      ###
+      # Caching.
+      # This actually *restores* a cache and schedules a cleanup action
+      # to save the cache. So it must come before the thing we want to use
+      # the cache.
+      ###
       - name: Get pip cache dir
         id: pip-cache
         run: |
@@ -225,7 +248,7 @@ jobs:
           coverage run -p -m unittest discover -s src
           PURE_PYTHON=1 coverage run -p -m unittest discover -s src
           coverage combine
-          coverage report -i
+          coverage report --ignore-errors --show-missing
       - name: Submit to Coveralls
         # This is a container action, which only runs on Linux.
         if: ${{ startsWith(runner.os, 'Linux') }}
@@ -243,7 +266,7 @@ jobs:
         parallel-finished: true
 
   docs:
-    needs: build-zope_interface
+    needs: build-package
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
@@ -257,6 +280,12 @@ jobs:
         uses: actions/setup-python@v2
         with:
           python-version: ${{ matrix.python-version }}
+      ###
+      # Caching.
+      # This actually *restores* a cache and schedules a cleanup action
+      # to save the cache. So it must come before the thing we want to use
+      # the cache.
+      ###
       - name: Get pip cache dir
         id: pip-cache
         run: |
@@ -279,8 +308,9 @@ jobs:
         run: |
           pip install -U wheel
           pip install -U coverage
-          pip install -U 'faulthandler; python_version == "2.7" and platform_python_implementation == "CPython"'
           pip install -U  "`ls dist/zope.interface-*.whl`[docs]"
+          # Until repoze.sphinx.autointerface supports Sphinx 4.x we cannot use it:
+          pip install -U "Sphinx < 4"
       - name: Build docs
         env:
           ZOPE_INTERFACE_STRICT_IRO: 1
@@ -290,7 +320,7 @@ jobs:
 
 
   lint:
-    needs: build-zope_interface
+    needs: build-package
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
@@ -304,7 +334,12 @@ jobs:
         uses: actions/setup-python@v2
         with:
           python-version: ${{ matrix.python-version }}
-
+      ###
+      # Caching.
+      # This actually *restores* a cache and schedules a cleanup action
+      # to save the cache. So it must come before the thing we want to use
+      # the cache.
+      ###
       - name: Get pip cache dir
         id: pip-cache
         run: |
@@ -351,6 +386,12 @@ jobs:
         uses: actions/setup-python@v2
         with:
           python-version: ${{ matrix.python-version }}
+      ###
+      # Caching.
+      # This actually *restores* a cache and schedules a cleanup action
+      # to save the cache. So it must come before the thing we want to use
+      # the cache.
+      ###
       - name: Get pip cache dir
         id: pip-cache
         run: |
@@ -408,16 +449,3 @@ jobs:
           password: ${{ secrets.TWINE_PASSWORD }}
           skip_existing: true
           packages_dir: wheelhouse/
-
-# TODO:
-# * Use YAML syntax to share snippets, like the old .travis.yml did
-# Sadly, as of 2021-02-01, Github Actions does not support anchors at
-# all. Just having an anchor results in an error:
-#
-#   The workflow is not valid. .github/workflows/tests.yml: Anchors
-#   are not currently supported. Remove the anchor 'an-strategy'
-#
-# The alternative of using composite actions doesn't work either,
-# because composite actions are limited to running shell scripts.
-# Steps in them can't call other actions with `uses:`, and nor can
-# they be conditional with `if:`.
diff --git a/.gitignore b/.gitignore
index 0a8d4e6..24ccc4e 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,24 +1,29 @@
-*.egg-info
+# Generated from:
+# https://github.com/zopefoundation/meta/tree/master/config/c-code
+*.egg-info/
+*.profraw
 *.pyc
 *.pyo
-*.so
-*.swp
-__pycache__
 .coverage
 .coverage.*
-.installed.cfg
-default.profraw
-nosetests.xml
-coverage.xml
-pyvenv.cfg
 .eggs/
+.installed.cfg
+.mr.developer.cfg
 .tox/
+.vscode/
+__pycache__/
 bin/
 build/
-eggs/
+coverage.xml
 develop-eggs/
-docs/_build/
+develop/
+dist/
+docs/_build
+eggs/
+etc/
 lib/
 lib64
+log/
 parts/
-htmlcov/
+pyvenv.cfg
+var/
diff --git a/.meta.toml b/.meta.toml
new file mode 100644
index 0000000..1c1e2d9
--- /dev/null
+++ b/.meta.toml
@@ -0,0 +1,117 @@
+# Generated from:
+# https://github.com/zopefoundation/meta/tree/master/config/c-code
+[meta]
+template = "c-code"
+commit-id = "3ddccc7a1430600364f48f37e4f24a275e1bbb85"
+
+[python]
+with-appveyor = true
+with-pypy = true
+with-legacy-python = true
+with-docs = false
+with-sphinx-doctests = false
+
+[tox]
+use-flake8 = false
+additional-envlist = [
+    "docs",
+    ]
+testenv-commands = [
+    "coverage run -p -m unittest discover -s src",
+    ]
+testenv-deps = [
+    ]
+testenv-setenv = [
+    "ZOPE_INTERFACE_STRICT_IRO=1",
+    ]
+testenv-additional = [
+    "",
+    "[testenv:docs]",
+    "basepython = python3",
+    "# Until repoze.sphinx.autointerface supports Sphinx 4.x we cannot use it:",
+    "deps =",
+    "    Sphinx < 4",
+    "    coverage",
+    "extras = docs",
+    "commands =",
+    "    sphinx-build -b html -d docs/_build/doctrees docs docs/_build/html",
+    "    coverage run -p -m sphinx -b doctest -d docs/_build/doctrees docs docs/_build/doctest",
+    ]
+coverage-command = "coverage combine"
+coverage-additional = [
+    "depends = py27,py27-pure,py35,py35-pure,py36,py36-pure,py37,py37-pure,py38,py38-pure,py39,py39-pure,pypy,pypy3,docs",
+    "parallel_show_output = true",
+    ]
+
+[coverage]
+fail-under = 99
+
+[manifest]
+additional-rules = [
+    "include *.cmd",
+    "include *.sh",
+    "include *.yml",
+    "include .coveragerc",
+    "recursive-include benchmarks *.py",
+    "recursive-include docs *.bat",
+    "recursive-include docs *.py",
+    "recursive-include docs *.rst",
+    "recursive-include docs Makefile",
+    ]
+
+[check-manifest]
+additional-ignores = [
+    "docs/_build/doctest/output.txt",
+    "docs/_build/html/_sources/*",
+    "docs/_build/html/_sources/api/*",
+    ]
+
+[github-actions]
+additional-install = [
+    "- name: Install zope.interface",
+    "  # ``python -m unittest discover`` only works with editable",
+    "  # installs, so we have to duplicate some work and can't",
+    "  # install the built wheel. (zope.testrunner",
+    "  # works fine with non-editable installs.)",
+    "  run: |",
+    "    pip install -U wheel",
+    "    pip install -U coverage",
+    "    pip install -U 'faulthandler; python_version == \"2.7\" and platform_python_implementation == \"CPython\"'",
+    "    # Unzip into src/ so that testrunner can find the .so files",
+    "    # when we ask it to load tests from that directory. This",
+    "    # might also save some build time?",
+    "    unzip -n dist/zope.interface-*whl -d src",
+    "    pip install -U -e .[test]",
+    "- name: Run tests and report coverage",
+    "  # Once with C extensions, once without. Yes, this runs them",
+    "  # twice on PyPy.",
+    "  run: |",
+    "    coverage run -p -m unittest discover -s src",
+    "    PURE_PYTHON=1 coverage run -p -m unittest discover -s src",
+    "    coverage combine",
+    "    coverage report --ignore-errors --show-missing",
+    ]
+
+[appveyor]
+global-env-vars = [
+    "global:",
+    "  TWINE_USERNAME: zope.wheelbuilder",
+    "  TWINE_PASSWORD:",
+    "    secure: UcdTh6W78cRLVGfKRFoa5A==",
+    ]
+build-script = [
+    "- python -W ignore setup.py -q bdist_wheel",
+    ]
+test-steps = [
+    "- python -m unittest discover -s src",
+    ]
+additional-lines = [
+    "artifacts:",
+    "  - path: 'dist\\*.whl'",
+    "    name: wheel",
+    "",
+    "deploy_script:",
+    "  - ps: if ($env:APPVEYOR_REPO_TAG -eq $TRUE) { pip install twine; twine upload --skip-existing dist/* }",
+    "",
+    "deploy: on",
+    ]
diff --git a/CHANGES.rst b/CHANGES.rst
index 55bbc84..6ce2b4d 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -5,7 +5,7 @@
 5.4.1 (unreleased)
 ==================
 
-- Nothing changed yet.
+- Add missing Trove classifier showing support for Python 3.9.
 
 
 5.4.0 (2021-04-15)
diff --git a/MANIFEST.in b/MANIFEST.in
index 83a0eb8..7f39b4e 100644
--- a/MANIFEST.in
+++ b/MANIFEST.in
@@ -1,21 +1,19 @@
+# Generated from:
+# https://github.com/zopefoundation/meta/tree/master/config/c-code
 include *.rst
 include *.txt
-include *.py
-include *.sh
-include .coveragerc
-include build.cmd
 include buildout.cfg
 include tox.ini
+include appveyor.yml
+include .coveragerc
 
-recursive-include docs *
-recursive-include src *
-
-global-exclude *.dll
-global-exclude *.pyc
-global-exclude *.pyo
-global-exclude *.so
-global-exclude coverage.xml
-global-exclude appveyor.yml
-
-prune docs/_build
-prune benchmarks
+recursive-include src *.py
+include *.cmd
+include *.sh
+include *.yml
+include .coveragerc
+recursive-include benchmarks *.py
+recursive-include docs *.bat
+recursive-include docs *.py
+recursive-include docs *.rst
+recursive-include docs Makefile
diff --git a/appveyor.yml b/appveyor.yml
index caca09e..d963129 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -1,4 +1,7 @@
+# Generated from:
+# https://github.com/zopefoundation/meta/tree/master/config/c-code
 environment:
+
   global:
     TWINE_USERNAME: zope.wheelbuilder
     TWINE_PASSWORD:
@@ -19,6 +22,7 @@ environment:
     - python: 39-x64
 
 install:
+  - "SET PYTHONVERSION=%PYTHON%"
   - "SET PATH=C:\\Python%PYTHON%;c:\\Python%PYTHON%\\scripts;%PATH%"
   - ps: |
       $env:PYTHON = "C:\\Python${env:PYTHON}"
@@ -28,8 +32,12 @@ install:
       }
   - ps: if (-not (Test-Path $env:PYTHON)) { throw "No $env:PYTHON" }
   - echo "C:\Program Files\Microsoft SDKs\Windows\v7.1\Bin\SetEnv.cmd" /x64 > "C:\Program Files (x86)\Microsoft Visual Studio 10.0\VC\bin\amd64\vcvars64.bat"
-  - python -m pip install -U pip setuptools wheel
-  - python -m pip install -U -e ".[test]"
+  - python -m pip install -U pip
+  - pip install -U setuptools wheel
+  - pip install -U -e .[test]
+
+matrix:
+  fast_finish: true
 
 build_script:
   - python -W ignore setup.py -q bdist_wheel
@@ -37,6 +45,8 @@ build_script:
 test_script:
   - python -m unittest discover -s src
 
+on_success:
+  - echo Build succesful!
 artifacts:
   - path: 'dist\*.whl'
     name: wheel
diff --git a/setup.cfg b/setup.cfg
index a9c2172..d3ac42a 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -1,21 +1,15 @@
-[nosetests]
-nocapture=1
-cover-package=zope.interface
-cover-erase=1
-cover-min-percentage=100
-cover-branches=1
-with-doctest=0
-where=src
-
-[aliases]
-dev = develop easy_install zope.interface[testing]
-docs = easy_install zope.interface[docs]
-
-[metadata]
-license_file = LICENSE.txt
-
+# Generated from:
+# https://github.com/zopefoundation/meta/tree/master/config/c-code
 [bdist_wheel]
-universal = 0
-
-[zest.releaser]
-create-wheel = no
+universal = 1
+
+[flake8]
+doctests = 1
+
+[check-manifest]
+ignore =
+    .editorconfig
+    .meta.toml
+    docs/_build/doctest/output.txt
+    docs/_build/html/_sources/*
+    docs/_build/html/_sources/api/*
diff --git a/setup.py b/setup.py
index eb846c6..b8b8b4a 100644
--- a/setup.py
+++ b/setup.py
@@ -120,6 +120,7 @@ setup(name='zope.interface',
           "Programming Language :: Python :: 3.6",
           "Programming Language :: Python :: 3.7",
           "Programming Language :: Python :: 3.8",
+          "Programming Language :: Python :: 3.9",
           "Programming Language :: Python :: Implementation :: CPython",
           "Programming Language :: Python :: Implementation :: PyPy",
           "Framework :: Zope :: 3",
diff --git a/src/zope/interface/tests/test_document.py b/src/zope/interface/tests/test_document.py
index bffe6a2..3e6dddd 100644
--- a/src/zope/interface/tests/test_document.py
+++ b/src/zope/interface/tests/test_document.py
@@ -124,7 +124,7 @@ class Test_asStructuredText(unittest.TestCase):
             """ This interface has a method.
             """
             def aMethod():
-                pass
+                pass  # pragma: no cover
 
         self.assertEqual(self._callFUT(IHasMethod), EXPECTED)
 
@@ -142,7 +142,7 @@ class Test_asStructuredText(unittest.TestCase):
             """ This interface has a method.
             """
             def aMethod(first, second):
-                pass
+                pass  # pragma: no cover
 
         self.assertEqual(self._callFUT(IHasMethod), EXPECTED)
 
@@ -160,7 +160,7 @@ class Test_asStructuredText(unittest.TestCase):
             """ This interface has a method.
             """
             def aMethod(first, second, *rest):
-                pass
+                pass  # pragma: no cover
 
         self.assertEqual(self._callFUT(IHasMethod), EXPECTED)
 
@@ -178,7 +178,7 @@ class Test_asStructuredText(unittest.TestCase):
             """ This interface has a method.
             """
             def aMethod(first, second, **kw):
-                pass
+                pass  # pragma: no cover
 
         self.assertEqual(self._callFUT(IHasMethod), EXPECTED)
 
@@ -221,9 +221,9 @@ class Test_asStructuredText(unittest.TestCase):
 
         class IBase(Interface):
             def method1():
-                pass
+                """docstring"""
             def method2():
-                pass
+                """docstring"""
 
         class IDerived(IBase):
             "IDerived doc"
@@ -233,7 +233,7 @@ class Test_asStructuredText(unittest.TestCase):
             def method3():
                 "method3 doc"
             def method4():
-                pass
+                pass  # pragma: no cover
             def method5():
                 "method5 doc"
 
@@ -348,7 +348,7 @@ class Test_asReStructuredText(unittest.TestCase):
             """ This interface has a method.
             """
             def aMethod():
-                pass
+                pass  # pragma: no cover
 
         self.assertEqual(self._callFUT(IHasMethod), EXPECTED)
 
@@ -366,7 +366,7 @@ class Test_asReStructuredText(unittest.TestCase):
             """ This interface has a method.
             """
             def aMethod(first, second):
-                pass
+                pass  # pragma: no cover
 
         self.assertEqual(self._callFUT(IHasMethod), EXPECTED)
 
@@ -384,7 +384,7 @@ class Test_asReStructuredText(unittest.TestCase):
             """ This interface has a method.
             """
             def aMethod(first, second, *rest):
-                pass
+                pass  # pragma: no cover
 
         self.assertEqual(self._callFUT(IHasMethod), EXPECTED)
 
@@ -402,7 +402,7 @@ class Test_asReStructuredText(unittest.TestCase):
             """ This interface has a method.
             """
             def aMethod(first, second, **kw):
-                pass
+                pass  # pragma: no cover
 
         self.assertEqual(self._callFUT(IHasMethod), EXPECTED)
 
@@ -445,9 +445,9 @@ class Test_asReStructuredText(unittest.TestCase):
 
         class IBase(Interface):
             def method1():
-                pass
+                pass  # pragma: no cover
             def method2():
-                pass
+                pass  # pragma: no cover
 
         class IDerived(IBase):
             "IDerived doc"
@@ -457,7 +457,7 @@ class Test_asReStructuredText(unittest.TestCase):
             def method3():
                 "method3 doc"
             def method4():
-                pass
+                pass  # pragma: no cover
             def method5():
                 "method5 doc"
 
diff --git a/src/zope/interface/tests/test_interface.py b/src/zope/interface/tests/test_interface.py
index 9dc2aff..1b793cd 100644
--- a/src/zope/interface/tests/test_interface.py
+++ b/src/zope/interface/tests/test_interface.py
@@ -1177,9 +1177,9 @@ class InterfaceTests(unittest.TestCase):
 
         class ICurrent(Interface):
             def method1(a, b):
-                pass
+                """docstring"""
             def method2(a, b):
-                pass
+                """docstring"""
 
         class IOther(Interface):
             pass
@@ -1207,7 +1207,7 @@ class InterfaceTests(unittest.TestCase):
         from zope.interface import providedBy
         class IBase(Interface):
             def method():
-                pass
+                """docstring"""
         class IDerived(IBase):
             pass
         class Current():
@@ -1230,7 +1230,7 @@ class InterfaceTests(unittest.TestCase):
 
         class IBase(Interface):
             def method():
-                pass
+                """docstring"""
 
         class IDerived(IBase):
             pass
@@ -1258,7 +1258,7 @@ class InterfaceTests(unittest.TestCase):
 
         class ILeft(Interface):
             def method():
-                pass
+                """docstring"""
 
         class IRight(ILeft):
             pass
@@ -1292,7 +1292,7 @@ class InterfaceTests(unittest.TestCase):
         class ILeft(Interface):
 
             def method():
-                pass
+                """docstring"""
 
         class IRight(ILeft):
             pass
@@ -1405,7 +1405,7 @@ class InterfaceTests(unittest.TestCase):
             attr = Attribute(u'My attr')
 
             def method():
-                pass
+                """docstring"""
 
         self.assertEqual(sorted(ISimple.names()), ['attr', 'method'])
 
@@ -1418,16 +1418,16 @@ class InterfaceTests(unittest.TestCase):
             attr = Attribute(u'My attr')
 
             def method():
-                pass
+                """docstring"""
 
         class IDerived(IBase):
             attr2 = Attribute(u'My attr2')
 
             def method():
-                pass
+                """docstring"""
 
             def method2():
-                pass
+                """docstring"""
 
         self.assertEqual(sorted(IDerived.names()),
                          ['attr2', 'method', 'method2'])
@@ -1753,7 +1753,7 @@ class InterfaceTests(unittest.TestCase):
 
         class ITagMe(Interface):
             def method():
-                pass
+                """docstring"""
             method.optional = 1
 
         method = ITagMe['method']
diff --git a/src/zope/interface/tests/test_verify.py b/src/zope/interface/tests/test_verify.py
index 8dbad97..5bceef6 100644
--- a/src/zope/interface/tests/test_verify.py
+++ b/src/zope/interface/tests/test_verify.py
@@ -69,7 +69,7 @@ class Test_verifyClass(unittest.TestCase):
 
         class ICurrent(Interface):
             def method():
-                pass
+                """docstring"""
 
         @implementer(ICurrent)
         class Current(object):
@@ -84,7 +84,7 @@ class Test_verifyClass(unittest.TestCase):
 
         class ICurrent(Interface):
             def method():
-                pass
+                """docstring"""
 
         @implementer(ICurrent)
         class Current(object):
@@ -101,7 +101,7 @@ class Test_verifyClass(unittest.TestCase):
 
         class IBase(Interface):
             def method():
-                pass
+                """docstring"""
 
         class IDerived(IBase):
             pass
@@ -119,7 +119,7 @@ class Test_verifyClass(unittest.TestCase):
 
         class IBase(Interface):
             def method():
-                pass
+                """docstring"""
 
         class IDerived(IBase):
             pass
@@ -140,7 +140,7 @@ class Test_verifyClass(unittest.TestCase):
         class ICurrent(Interface):
 
             def method(a):
-                pass
+                """docstring"""
 
         @implementer(ICurrent)
         class Current(object):
@@ -158,7 +158,7 @@ class Test_verifyClass(unittest.TestCase):
         class ICurrent(Interface):
 
             def method(a):
-                pass
+                """docstring"""
 
         @implementer(ICurrent)
         class Current(object):
@@ -177,7 +177,7 @@ class Test_verifyClass(unittest.TestCase):
         class ICurrent(Interface):
 
             def method(*args):
-                pass
+                """docstring"""
 
         @implementer(ICurrent)
         class Current(object):
@@ -196,7 +196,7 @@ class Test_verifyClass(unittest.TestCase):
         class ICurrent(Interface):
 
             def method(**kw):
-                pass
+                """docstring"""
 
         @implementer(ICurrent)
         class Current(object):
@@ -215,7 +215,7 @@ class Test_verifyClass(unittest.TestCase):
         class ICurrent(Interface):
 
             def method(a):
-                pass
+                """docstring"""
 
         @implementer(ICurrent)
         class Current(object):
@@ -233,7 +233,7 @@ class Test_verifyClass(unittest.TestCase):
         class ICurrent(Interface):
 
             def method(a):
-                pass
+                """docstring"""
 
         @implementer(ICurrent)
         class Current(object):
@@ -250,7 +250,7 @@ class Test_verifyClass(unittest.TestCase):
         class ICurrent(Interface):
 
             def method(a):
-                pass
+                """docstring"""
 
         @implementer(ICurrent)
         class Current(object):
@@ -268,7 +268,7 @@ class Test_verifyClass(unittest.TestCase):
         class ICurrent(Interface):
 
             def method(a):
-                pass
+                """docstring"""
 
         @implementer(ICurrent)
         class Current(object):
@@ -286,7 +286,7 @@ class Test_verifyClass(unittest.TestCase):
         class ICurrent(Interface):
 
             def method(a):
-                pass
+                """docstring"""
 
         @implementer(ICurrent)
         class Current(object):
@@ -303,7 +303,7 @@ class Test_verifyClass(unittest.TestCase):
         class ICurrent(Interface):
 
             def method(a):
-                pass
+                """docstring"""
 
         @implementer(ICurrent)
         class Current(object):
@@ -321,7 +321,7 @@ class Test_verifyClass(unittest.TestCase):
         class ICurrent(Interface):
 
             def method(a, *args):
-                pass
+                """docstring"""
 
         @implementer(ICurrent)
         class Current(object):
@@ -339,7 +339,7 @@ class Test_verifyClass(unittest.TestCase):
         class ICurrent(Interface):
 
             def method(a, *args):
-                pass
+                """docstring"""
 
         @implementer(ICurrent)
         class Current(object):
@@ -356,7 +356,7 @@ class Test_verifyClass(unittest.TestCase):
         class ICurrent(Interface):
 
             def method(a, *args):
-                pass
+                """docstring"""
 
         @implementer(ICurrent)
         class Current(object):
@@ -373,7 +373,7 @@ class Test_verifyClass(unittest.TestCase):
         class ICurrent(Interface):
 
             def method(**kwargs):
-                pass
+                """docstring"""
 
         @implementer(ICurrent)
         class Current(object):
@@ -391,7 +391,7 @@ class Test_verifyClass(unittest.TestCase):
         class ICurrent(Interface):
 
             def method(*args):
-                pass
+                """docstring"""
 
         @implementer(ICurrent)
         class Current(object):
@@ -411,7 +411,7 @@ class Test_verifyClass(unittest.TestCase):
         class ICurrent(Interface):
 
             def method(**kwargs):
-                pass
+                """docstring"""
 
         @implementer(ICurrent)
         class Current(object):
@@ -446,7 +446,7 @@ class Test_verifyClass(unittest.TestCase):
 
         class ICurrent(Interface):
             def method():
-                pass
+                """docstring"""
 
         @implementer(ICurrent)
         class Current:
@@ -519,7 +519,7 @@ class Test_verifyClass(unittest.TestCase):
         class ICurrent(Interface):
 
             def method(a):
-                pass
+                """docstring"""
 
         @implementer(ICurrent)
         class Current(object):
diff --git a/tox.ini b/tox.ini
index 3394e79..026d567 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,67 +1,63 @@
+# Generated from:
+# https://github.com/zopefoundation/meta/tree/master/config/c-code
 [tox]
+minversion = 3.18
 envlist =
-    py27,py27-pure,
-    py35,py35-pure,
-    py36,
-    py37,
-    py38,py38-cext,
-    py39,
-    pypy,
-    pypy3,
-    coverage,
+    lint
+    py27,py27-pure
+    py35,py35-pure
+    py36,py36-pure
+    py37,py37-pure
+    py38,py38-pure
+    py39,py39-pure
+    pypy
+    pypy3
+    coverage
     docs
-# NB: if you add new environments, please also add them to depends in
-# testenv:coverage so that parallel runs (tox -p auto) will work correctly
 
 [testenv]
-# ``usedevelop`` is required otherwise unittest complains that it
-# discovers a file in src/... but imports it from .tox/.../
-# ``skip_install`` also basically works, but that causes the ``extras``
-# not to be installed (though ``deps`` still are), and doesn't
-# rebuild C extensions.
 usedevelop = true
-commands =
-    coverage run -p -m unittest discover -s src
-extras = test
+deps =
 setenv =
+    pure: PURE_PYTHON=1
+    !pure-!pypy-!pypy3: PURE_PYTHON=0
     ZOPE_INTERFACE_STRICT_IRO=1
+commands =
+    coverage run -p -m unittest discover -s src
+extras =
+    test
 
-[testenv:py27-pure]
-setenv =
-    PURE_PYTHON=1
-
-[testenv:py35-pure]
-setenv =
-    PURE_PYTHON=1
-
-[testenv:py38-cext]
-# Require the C extension
-setenv =
-    PURE_PYTHON=0
-
-[testenv:py]
+[testenv:docs]
+basepython = python3
+# Until repoze.sphinx.autointerface supports Sphinx 4.x we cannot use it:
+deps =
+    Sphinx < 4
+    coverage
+extras = docs
 commands =
-    python --version
-    {[testenv]commands}
+    sphinx-build -b html -d docs/_build/doctrees docs docs/_build/html
+    coverage run -p -m sphinx -b doctest -d docs/_build/doctrees docs docs/_build/doctest
 
 [testenv:coverage]
-# The -i/--ignore arg is necessary; we get
-# No source for code: '//.tox/pypy/site-packages/zope/interface/__init__.py'
-# without it.
+basepython = python3
+allowlist_externals =
+    mkdir
+deps =
+    coverage
 commands =
+    mkdir -p {toxinidir}/parts/htmlcov
     coverage combine
-    coverage report -i
     coverage html -i
-    coverage xml -i
-depends = py27,py27-pure,py35,py35-pure,py36,py37,py38,py38-cext,py39,pypy,pypy3,docs
+    coverage report -i -m --fail-under=99
+depends = py27,py27-pure,py35,py35-pure,py36,py36-pure,py37,py37-pure,py38,py38-pure,py39,py39-pure,pypy,pypy3,docs
 parallel_show_output = true
 
-[testenv:docs]
-basepython =
-    python3
-commands =
-    sphinx-build -b html -d docs/_build/doctrees docs docs/_build/html
-    coverage run -p -m sphinx -b doctest -d docs/_build/doctrees docs docs/_build/doctest
+[testenv:lint]
+basepython = python3
+skip_install = true
 deps =
-    Sphinx
-    repoze.sphinx.autointerface
+    check-manifest
+    check-python-versions
+commands =
+    check-manifest
+    check-python-versions