@python_2_unicode_compatible
class AbstractBaseUser(models.Model):
    password = models.CharField(_('password'), max_length=128)
    last_login = models.DateTimeField(_('last login'), default=timezone.now)

    is_active = True

    REQUIRED_FIELDS = []

    class Meta:
        abstract = True

    def get_username(self):
        "Return the identifying username for this User"
        return getattr(self, self.USERNAME_FIELD)

    def __str__(self):
        return self.get_username()

    def natural_key(self):
        return (self.get_username(),)

    def is_anonymous(self):
        """
        Always returns False. This is a way of comparing User objects to
        anonymous users.
        """
        return False

    def is_authenticated(self):
        """
        Always return True. This is a way to tell if the user has been
        authenticated in templates.
        """
        return True

    def set_password(self, raw_password):
        self.password = make_password(raw_password)

    def check_password(self, raw_password):
        """
        Returns a boolean of whether the raw_password was correct. Handles
        hashing formats behind the scenes.
        """
        def setter(raw_password):
            self.set_password(raw_password)
            self.save(update_fields=["password"])
        return check_password(raw_password, self.password, setter)

    def set_unusable_password(self):
        # Sets a value that will never be a valid hash
        self.password = make_password(None)

    def has_usable_password(self):
        return is_password_usable(self.password)

    def get_full_name(self):
        raise NotImplementedError()

    def get_short_name(self):
        raise NotImplementedError()