python - django框架使用自定义的类

1.我想用自定义的User类，而不想用默认User类，按照官方文档的demo做了下（https://docs.djangoproject.com/en/1.9/topics/auth/customizing/#auth-custom-user），各种奇怪的问题，找不到属性什么的。
下面是我的demo：

from __future__ import unicode_literals

from django.db import models

from django.contrib.auth.models import AbstractBaseUser

from django.contrib.auth.models import BaseUserManager


# Create your models here.

class UserManager(BaseUserManager):
    """
    test custom user manager
    """


    def __init__(self):
        pass

    def create_user(self, username, password=None):
        """
        create user
        :param username:
        :param password:
        :return:
        """
        if not username:
            raise ValueError('User must have an username')

        user = self.model(username=username)
        user.set_password(password)
        user.save(using=self._db)
        return user

    def create_superuser(self, username, password):
        """
        create superuser
        :param username:
        :param password:
        :return:
        """
        user = self.create_user(username=username, password=password)
        user.is_admin = True
        user.save(using=self._db)
        return user


class User(AbstractBaseUser):
    """
    test custom user model
    """

    def __init__(self):
        pass

    username = models.CharField(max_length=128, unique=True)
    # is_admin = models.BooleanField(default=False)

    objects = UserManager()       

    USERNAME_FIELD = "username"  #username列

    class Meta:
        db_table = "testdata_user"  #表名

报错就是

AttributeError: 'UserManager' object has no attribute 'name'

调了很久也google过，就是不知道哪里错了，没头绪，请教下各位在生产下自定义User类的经验，能够指出小弟的错误，最好可以给出个demo，让我看看我哪里弄错了。感激不尽