Fix virtualenv setuptools version bug (#549)

* Use SETUPTOOLS_USE_DISTUTILS env var rather than pinning virtualenv

* Add explanatory comment and fix typo

* Add a further explanatory comment for traceability

* Add the SETUPTOOLS_USE_DISTUTILS env var to the nox lint session

* Add session.posargs back to the lint session

.github/workflows/ci.yml

@@ -3,6 +3,9 @@ on: [push, pull_request]
 env:
   FORCE_COLOR: "1"
   PRE_COMMIT_COLOR: "always"
+  # See https://github.com/theacodes/nox/issues/545
+  # and https://github.com/pre-commit/pre-commit/issues/2178#issuecomment-1002163763
+  SETUPTOOLS_USE_DISTUTILS: "stdlib"
 jobs:
   build:
     runs-on: ${{ matrix.os }}

noxfile.py

@@ -93,11 +93,16 @@ def cover(session):
 @nox.session(python="3.9")
 def lint(session):
     """Run pre-commit linting."""
-    # Pin virtualenv for pre-commit run
+    session.install("pre-commit")
     # See https://github.com/theacodes/nox/issues/545
-    session.install("virtualenv==20.10.0", "pre-commit")
+    # and https://github.com/pre-commit/pre-commit/issues/2178#issuecomment-1002163763
     session.run(
-        "pre-commit", "run", "--all-files", "--show-diff-on-failure", *session.posargs
+        "pre-commit",
+        "run",
+        "--all-files",
+        "--show-diff-on-failure",
+        env={"SETUPTOOLS_USE_DISTUTILS": "stdlib"},
+        *session.posargs,
     )