Change user's login email
        :param user: AuthUser
        :param email:
        :return:

def change_username(self, username):
        """
        Change user's login email
        :param user: AuthUser
        :param email:
        :return:
        """

        def cb():

            if self.login_method == "username" and "@" in username:
                raise exceptions.AuthError(_("Username can't be an email"))
            elif self.login_method == "email" and "@" not in username:
                raise exceptions.AuthError(_("Invalid email login"))
            if "@" in username:
                if not utils.is_email_valid(username):
                    raise exceptions.AuthError("Email address invalid")
            elif not utils.is_username_valid(username):
                raise exceptions.AuthError("Username invalid")

            # Change both email and
            if self.login_method == "email":
                if not models.AuthUser.get_by_username(username) \
                        and not models.AuthUser.get_by_email(username):
                    self.user.change_username(username)
                    self.user.change_email(username)
            else:
                self.user.change_username(username)
            return username

        return signals.user_update(self, ACTIONS["USERNAME"], cb)