Fixed #10414 -- Make select_related fail on invalid field names.

https://code.djangoproject.com/ticket/10414

This is basically my first non-trivial contribution to Django, so it might not be perfect. I'll be happy to update the PR as required. :)
I think if you check `setup.cfg` for the project, it explicitly switches off E128 checks. Don't think it's too big of a deal either way :).