fix: Set PYTHONPATH in GH actions workflow

Author: joolean

.github/workflows/ci.yml

@@ -67,6 +67,7 @@ jobs:
           poetry install
       - name: Run pytest
         env:
+          PYTHONPATH: ${{ github.workspace }}
           PGPORT: ${{ job.services.postgres.ports['5432'] }}
         run: poetry run pytest --ds tests.settings