attempt to fix the package testing

.github/workflows/python-package.yml

@@ -23,6 +23,7 @@ jobs:
       run: |
         python -m pip install --upgrade pip
         python -m pip install flake8 pytest pytest-cov
+        if [ -f requirements.txt ]; then pip install -r requirements.txt; fi
         python -m pip install -e .
     - name: Lint with flake8
       run: |