old_contents: from django.contrib.auth.models import User
  from django_fbi.backends.default import DefaultBackend
  
  class SimpleBackend(DefaultBackend):
      def _register_user(self):
          ''' Simple registration for sites that use email for auth. Users are
              created with the username "FB_<facebook_id>", logged in, and
              redirected. Requires 'email' permission from Facebook.
          '''
          self.user = User.objects.create(
              username='FB_%s' % self.facebook.profile['id'],
              email=self.facebook.profile['email']
              )
          profile = self._get_user_profile()
          profile.facebook_id = self.facebook.profile['id']
          profile.facebook_email = self.facebook.profile['email']
          profile.save()
          self._authenticate_user() ## need a User object with .backend
          return self._login_user(reconnect=True)
  
new_contents: from django.contrib.auth.models import User
  from django_fbi.backends.default import DefaultBackend
  
  class SimpleBackend(DefaultBackend):
      def _register_user(self):
          ''' Simple registration for sites that use email for auth. Users are
              created with the username "FB_<facebook_id>", logged in, and
              redirected. Requires 'email' permission from Facebook.
          '''
          self.user = User(
              username='FB_%s' % self.facebook.profile['id'],
              email=self.facebook.profile['email']
              )
          self.user.set_unusable_password()
          self.user.save()
          profile = self._get_user_profile()
          profile.facebook_id = self.facebook.profile['id']
          profile.facebook_email = self.facebook.profile['email']
          profile.save()
          self._authenticate_user() ## need a User object with .backend
          return self._login_user(reconnect=True)
  
subject: set an unusable password when the user is created