Install "pytest-cov" to support "pytest --cov"

.github/workflows/python-package.yml

@@ -27,7 +27,7 @@ jobs:
       - name: Install dependencies
         run: |
           python -m pip install --upgrade pip
-          python -m pip install --upgrade black pyright pytest
+          python -m pip install --upgrade black pyright pytest pytest-cov
       - name: Format with black
         run: |
           black --diff .