Merge pull request #2040 from EliahKagan/mypy-free-threaded

Fix CI `mypy` command on free-threaded Python

Author: EliahKagan

.github/workflows/pythonpackage.yml

@@ -97,10 +97,11 @@ jobs:
 
     - name: Check types with mypy
       run: |
-        mypy --python-version=${{ matrix.python-version }}
+        mypy --python-version="${PYTHON_VERSION%t}"  # Version only, with no "t" for free-threaded.
       env:
         MYPY_FORCE_COLOR: "1"
         TERM: "xterm-256color"  # For color: https://github.com/python/mypy/issues/13817
+        PYTHON_VERSION: ${{ matrix.python-version }}
       # With new versions of mypy new issues might arise. This is a problem if there is
       # nobody able to fix them, so we have to ignore errors until that changes.
       continue-on-error: true