[bugfix] add poetry pytest command

Author: CuriousGu

.github/workflows/python-app.yml

@@ -29,7 +29,7 @@ jobs:
         pip install poetry
         poetry lock
         poetry install
-        pip install flake8
+        pip install flake8 pytest
     - name: Test with pytest
       run: |
-        PYTHONPATH=$PYTHONPATH:$(pwd) pytest
+        poetry run pytest