def add_group_maintainer(self, name, user):
        """Add the given user to the named group.

        Both group and user must already exist for this to succeed.

        Args:
            name (string): Name of group.
            user (string): User to add to group.
            version (optional[string]): Version of the Boss API to use.  Defaults to the latest supported version.

        Raises:
            requests.HTTPError on failure.
        """
        self.service.add_group_maintainer(
            name, user, self.url_prefix, self.auth, self.session,
            self.session_send_opts)