Add pre-commit hook and use in CI.

docs/internals/testing.md

@@ -11,4 +11,4 @@ You can either tweak the ``tests/test_project/settings.py`` file to get your DB
 ## Database setup
 
 By default, the test Django project in the repository has multiple databases configured in order to make the CI tests work.
-Do not hesitate to modify [the configured test databases](../../tests/test_project/settings.py).
+Do not hesitate to modify [the configured test databases](../../tests/test_project/settings.py).