turned on F7 warnings for flake8

.github/workflows/pytest_flake8.yml

@@ -32,6 +32,6 @@ jobs:
     - name: Lint with flake8
       run: |
         # stop the build if there are Python syntax errors
-        flake8 . --count --select=E9,F63 --show-source --statistics
+        flake8 . --count --select=E9,F63,F7 --show-source --statistics
         # exit-zero treats all errors as warnings. The GitHub editor is 127 chars wide
         #flake8 . --count --exit-zero --max-complexity=10 --max-line-length=127 --statistics