GH actions: use python -m pytest

Author: tschaume

.github/workflows/pull-request.yml

@@ -30,8 +30,8 @@ jobs:
           python${{ matrix.python-version }} -m piptools sync requirements/ubuntu-latest_py${{ matrix.python-version }}_extras.txt
           python${{ matrix.python-version }} -m pip install --no-deps .
       - name: Test modules
-        run: pytest tests
+        run: python${{ matrix.python-version }} -m pytest tests
       - name: Test example apps
         env:
           PERCY_TOKEN: ${{ secrets.PERCY_TOKEN }}
-        run: pytest --color=yes --webdriver Chrome --headless crystal_toolkit/apps/examples/tests/
+        run: python${{ matrix.python-version }} -m pytest --color=yes --webdriver Chrome --headless crystal_toolkit/apps/examples/tests/