Fix flake8 pre-commit hook running through PyCharm

.pre-commit-config.yaml

@@ -21,6 +21,6 @@ repos:
         name: Flake8
         description: This hook runs flake8 within our project's pipenv environment.
         entry: pipenv run flake8
-        language: python
+        language: system
         types: [python]
         require_serial: true