def delete_group_maintainer(self, grp_name, user):
        """
        Delete 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.

        Raises:
            requests.HTTPError on failure.
        """
        self.project_service.set_auth(self._token_project)
        self.project_service.delete_group_maintainer(grp_name, user)