code: def create_lazy_user(self):
          
          user_class = self.model.get_user_class()
          username = self.generate_username(user_class)
          user = user_class.objects.create_user(username, '')
          self.create(user=user)
          return user, username
docs: Create a lazy user. Returns a 2-tuple of the underlying User
          object (which may be of a custom class), and the username.