install coverage in workflow

.github/workflows/python-package.yml

@@ -26,7 +26,7 @@ jobs:
             - name: Install dependencies
               run: |
                   python -m pip install --upgrade pip
-                  python -m pip install flake8 pytest requests-mock
+                  python -m pip install flake8 pytest requests-mock coverage
                   if [ -f requirements.txt ]; then pip install -r requirements.txt; fi
             - name: Lint with flake8
               run: |