Django 1.9.6 Case Insensitive Username Logins

managers.py

from django.db.models.functions import Lower
from django.db.models import CharField
from django.contrib.auth.models import UserManager as DjangoUserManager

CharField.register_lookup(Lower, 'lower')


class UserManager(DjangoUserManager):
    """
    Allow case insensitive usernames for authenticating.
    Use this Model Manager on your Custom User Model.
    
    ie. objects = UserManager()
    
    """

    def get_by_natural_key(self, username):
        username_lower = username.lower()
        return self.get(
            username__lower=username_lower
        )