Merge branch '3.1.x'

diff --cc .github/workflows/tests.yaml
index 85e748b640871897ffcf6aae042bc1f2422cd394,a85f6c7b3a4f00d866d58d4619df051db09b3ad2..81787304bfee55050d1a2e94a5960a8dda853690
--- 1/.github/workflows/tests.yaml
--- 2/.github/workflows/tests.yaml
+++ b/.github/workflows/tests.yaml
@@@ -47,10 -47,10 +47,10 @@@ jobs
            pip install -U setuptools
            python -m pip install -U pip
        - name: cache mypy
-         uses: actions/cache@v3
+         uses: actions/cache@58c146cc91c5b9e778e71775dfe9bf1442ad9a12
          with:
            path: ./.mypy_cache
 -          key: mypy|${{ matrix.python }}|${{ hashFiles('setup.cfg') }}
 +          key: mypy|${{ matrix.python }}|${{ hashFiles('pyproject.toml') }}
          if: matrix.tox == 'typing'
        - run: pip install tox
        - run: tox run -e ${{ matrix.tox }}