Test SETUPTOOLS_USE_DISTUTILS = stdlib, local on GH Actions

.github/workflows/main.yml

@@ -6,6 +6,9 @@ jobs:
   test:
     strategy:
       matrix:
+        distutils:
+        - stdlib
+        - local
         python:
         - pypy3
         - 3.6
@@ -16,6 +19,8 @@ jobs:
         - macos-latest
         - windows-latest
     runs-on: ${{ matrix.platform }}
+    env:
+      SETUPTOOLS_USE_DISTUTILS: ${{ matrix.distutils }}
     steps:
       - uses: actions/checkout@v2
       - name: Setup Python

pytest.ini

@@ -34,3 +34,15 @@ filterwarnings=
 
 	# https://github.com/pypa/setuptools/issues/2497
 	ignore:.* is an invalid version and will not be supported::pkg_resources
+
+	# https://github.com/pypa/setuptools/pull/2865#issuecomment-965700112
+	# ideally would apply to Python 3.10+ when
+	# SETUPTOOLS_USE_DISTUTILS=stdlib but for
+	# https://github.com/pytest-dev/pytest/discussions/9296
+	ignore:The distutils.sysconfig module is deprecated, use sysconfig instead
+
+	# Workaround for pypa/setuptools#2868
+	# ideally would apply to PyPy only but for
+	# https://github.com/pytest-dev/pytest/discussions/9296
+	ignore:Distutils was imported before setuptools
+	ignore:Setuptools is replacing distutils

setup.cfg

@@ -55,11 +55,11 @@ testing =
 	mock
 	flake8-2020
 	virtualenv>=13.0.0
-	pytest-virtualenv>=1.2.7
+	pytest-virtualenv @ git+https://github.com/jaraco/pytest-plugins@distutils-deprecated#subdirectory=pytest-virtualenv
 	wheel
 	paver
 	pip>=19.1 # For proper file:// URLs support.
-	jaraco.envs
+	jaraco.envs>=2.2
 	pytest-xdist
 	sphinx
 	jaraco.path>=3.2.0

setuptools/tests/test_distutils_adoption.py

@@ -14,6 +14,11 @@
 
 class VirtualEnv(jaraco.envs.VirtualEnv):
     name = '.env'
+    # Some version of PyPy will import distutils on startup, implicitly
+    # importing setuptools, and thus leading to BackendInvalid errors
+    # when upgrading Setuptools. Bypass this behavior by avoiding the
+    # early availability and need to upgrade.
+    create_opts = ['--no-setuptools']
 
     def run(self, cmd, *args, **kwargs):
         cmd = [self.exe(cmd[0])] + cmd[1:]

setuptools/tests/test_virtualenv.py

@@ -89,6 +89,10 @@ def skip_network(param):
     return list(versions)
 
 
+@pytest.mark.skipif(
+    'platform.python_implementation() == "PyPy"',
+    reason="https://github.com/pypa/setuptools/pull/2865#issuecomment-965834995",
+)
 @pytest.mark.parametrize('pip_version', _get_pip_versions())
 def test_pip_upgrade_from_source(pip_version, tmp_src, virtualenv):
     """

tox.ini

@@ -15,6 +15,7 @@ commands =
 usedevelop = True
 extras = testing
 passenv =
+	SETUPTOOLS_USE_DISTUTILS
 	windir  # required for test_pkg_resources
 
 [testenv:docs]