HTTPError 403 (Forbidden) with Django and python-social-auth connecting to Google with OAuth2

This answer is outdated as the Google+ API is being deprecated on 3/7/19

You need to add the Google+ API to the list of enabled APIs on the Google Developer Console (under APIs)

Note: If you want to see the real error message, use the traceback to look at the content of the response variable (response.text). I use werkzeug for that (django-extensions + python manage.py runserver_plus).