old_contents: from django.db import models
  from django.contrib.auth.models import AbstractBaseUser, PermissionsMixin
  
  
  class User(AbstractBaseUser, PermissionsMixin):
      email = models.EmailField(unique=True)
  
      USERNAME_FIELD = 'email'
  
      def __init__(self, *args, **kwargs):
          super(User, self).__init__(*args, **kwargs)
  
          self.set_unusable_password()
  
new_contents: from django.db import models
  from django.contrib.auth.models import (
      BaseUserManager, AbstractBaseUser, PermissionsMixin)
  
  
  class UserManager(BaseUserManager):
      def create_user(self, email):
          if not email:
              raise ValueError('Users must have an email address')
  
          user = self.model(
              email=self.normalize_email(email)
          )
  
          user.save(using=self._db)
          return user
  
  
  class User(AbstractBaseUser, PermissionsMixin):
      email = models.EmailField(unique=True)
  
      objects = UserManager()
  
      USERNAME_FIELD = 'email'
  
      def __init__(self, *args, **kwargs):
          super(User, self).__init__(*args, **kwargs)
  
          self.set_unusable_password()
  
subject: Add user manager to pass token tests