def add_user(
        self, user, first_name=None, last_name=None, email=None, password=None):
        """Add a new user.

        Args:
            user (string): User name.
            first_name (optional[string]): User's first name.  Defaults to None.
            last_name (optional[string]): User's last name.  Defaults to None.
            email: (optional[string]): User's email address.  Defaults to None.
            password: (optional[string]): User's password.  Defaults to None.

        Raises:
            requests.HTTPError on failure.
        """
        self.service.add_user(
            user, first_name, last_name, email, password,
            self.url_prefix, self.auth, self.session, self.session_send_opts)