这个问题通常发生在使用Django自带的User模型扩展中，用户自定义模型的元数据可能未正确声明继承自AbstractBaseUser和PermissionsMixin。应该在扩展User模型时使用如下代码：

from django.contrib.auth.models import AbstractBaseUser, BaseUserManager, PermissionsMixin

class MyUserManager(BaseUserManager):
    def create_user(self, email, password=None, **extra_fields):
        if not email:
            raise ValueError('The Email field must be set')
        user = self.model(email=self.normalize_email(email), **extra_fields)
        user.set_password(password)
        user.save(using=self._db)
        return user

    def create_superuser(self, email, password, **extra_fields):
        extra_fields.setdefault('is_staff', True)
        extra_fields.setdefault('is_superuser', True)
        return self.create_user(email, password, **extra_fields)

class MyUser(AbstractBaseUser, PermissionsMixin):
    email = models.EmailField(unique=True)
    is_staff = models.BooleanField(default=False)
    first_name = models.CharField(max_length=30)
    last_name = models.CharField(max_length=30)
    date_joined = models.DateTimeField(auto_now_add=True)

    objects = MyUserManager()

    USERNAME_FIELD = 'email'
    REQUIRED_FIELDS = ['first_name', 'last_name']

    def get_full_name(self):
        return f"{self.first_name} {self.last_name}"

    def get_short_name(self):
        return self.first_name

这样定义用户模型可实现用户的登录和认证等系统功能。具体的model可以根据实际情况进行更改。