added venv activation to pytest step because existence is pain

Author: RidleyLarsen

.github/workflows/pythonpackage.yml

@@ -34,4 +34,5 @@ jobs:
         flake8 . --count --max-complexity=10 --max-line-length=127 --statistics
     - name: Test with pytest
       run: |
+        source .venv/bin/activate
         pytest