I was getting this facebook login error:

URL Blocked 
  This redirect failed because the redirect URI is not
  whitelisted in the app’s Client OAuth Settings. Make sure Client and
  Web OAuth Login are on and add all your app domains as Valid OAuth
  Redirect URIs.

Facebook login requires whitelisting of the call-back url.
what is the call back url for django-social-auth or  python-social-auth ?
include a url to your website that is the absolute url version of this relative url:
/complete/facebook/
how to find this out?
use Chrome browser dev tools, enable preserve log, try to login to your app.
This question / answer is for django-social-auth but likely applies to python-social-auth too.
python-social-auth and facebook login: what is the whitelist redirect url to include in fb configuration?