class CUserManager(BaseUserManager):

        def _create_user(self, email, first_name, password,
                         is_staff, is_superuser, **extra_fields):
            """
        Creates and saves a User with the given email and password.
        """
        now = timezone.now()
        if not email:
            raise ValueError('The given email must be set')
        email = self.normalize_email(email)
        user = self.model(email=email,
                          first_name = first_name,
                          is_staff=is_staff, is_active=False,
                          is_superuser=is_superuser, last_login=now,
                          date_joined=now, **extra_fields)
        user.set_password(password)
        user.save(using=self._db)
        return user

    def create_user(self, email, first_name, password=None, **extra_fields):
        return self._create_user(email, first_name, password, False, False,
                                 **extra_fields)

    def create_superuser(self, email, first_name, password, **extra_fields):
        return self._create_user(email, first_name, password, True, True,
                                 **extra_fields)


class CUser(AbstractBaseUser, PermissionsMixin):
    email = models.EmailField(_('email address'), max_length=254, unique=True)
    first_name = models.CharField(_('first name'), max_length=30)
    last_name = models.CharField(_('last name'), max_length=30, blank=True)
    is_staff = models.BooleanField(_('staff status'), default=False,
        help_text=_('Designates whether the user can log into this admin '
                    'site.'))
    is_active = models.BooleanField(_('active'), default=False,
        help_text=_('Designates whether this user should be treated as '
                    'active. Unselect this instead of deleting accounts.'))
    date_joined = models.DateTimeField(_('date joined'), default=timezone.now)
    last_updated = models.DateTimeField(_('last updated'), default=timezone.now)

    objects = CUserManager()

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

>>> from django.contrib.auth import get_user_model, auhtenticate
>>> u = get_user_model()
>>> authenticate(username='abc@gmail.com', password='abc)