Update python-app.yml

fix pytest call to use python -m

Author: poldrack

.github/workflows/python-app.yml

@@ -33,4 +33,4 @@ jobs:
         flake8 . --count --exit-zero --max-complexity=10 --max-line-length=127 --statistics
     - name: Test with pytest
       run: |
-        pytest
+        python -m pytest