Remove a user from a group.

        :param username: The user to remove from the group.
        :param groupname: The group that the user will be removed from.

def remove_user_from_group(self, username, groupname):
        """Remove a user from a group.

        :param username: The user to remove from the group.
        :param groupname: The group that the user will be removed from.
        """
        url = self._options['server'] + '/rest/api/latest/group/user'
        x = {'groupname': groupname,
             'username': username}

        self._session.delete(url, params=x)

        return True