Need to clear caches in `django.db.connections` during `django_db_modify_db_settings`?

ConnectionHandler (django.db.connections is an instance of this) caches, so I ended up with with problems due to using connection from the old config† after changing settings from a django_db_modify_db_settings fixture. I fixed my issue by calling the following code before+after the fixture:

def clear_caches():
    """Invalidate the connection caches."""
    connections._connections = threading.local()
    # this will clear the cached property
    del connections.databases

If there isn't any disagreement I will submit a PR for this to change the default fixture and also update the documentation.

This looks like it should work back to at least 1.7.x, I haven't checked back further. Is there an officially supported range of Django versions?

† in my case I was only getting the database which was configured in DJANGO_SETTINGS_MODULE, I am not sure if that was because of app code causing a query too soon, or if it is expected every time in Django (in 1.11.11)

Start by reviewing the django_db_modify_db_settings fixture and the referenced ConnectionHandler implementation in django/db/utils.py. Determine the supported Django version range and whether the default fixture should clear these caches, then update the documentation if that behavior is adopted.