Add back mypy strict test

Author: ShaneHarvey

.github/workflows/test-python.yml

@@ -68,6 +68,9 @@ jobs:
           mypy --install-types --non-interactive --disable-error-code var-annotated --disable-error-code attr-defined --disable-error-code union-attr --disable-error-code assignment --disable-error-code no-redef --disable-error-code index --allow-redefinition --allow-untyped-globals --exclude "test/mypy_fails/*.*" test
           python -m pip install -U typing_extensions
           mypy --install-types --non-interactive test/test_typing.py test/test_typing_strict.py
+      - name: Run mypy strict
+        run: |
+          mypy --strict test/test_typing_strict.py
       - name: Run pyright
         run: |
           python -m pip install -U pip pyright==1.1.290