Remove a subscriber from this workitem

        If the subscriber has not been added, no more actions will be
        performed.

        :param email: the subscriber's email

def removeSubscriber(self, email):
        """Remove a subscriber from this workitem

        If the subscriber has not been added, no more actions will be
        performed.

        :param email: the subscriber's email
        """

        headers, raw_data = self._perform_subscribe()
        missing_flag, raw_data = self._remove_subscriber(email, raw_data)
        if missing_flag:
            return

        self._update_subscribe(headers, raw_data)
        self.log.info("Successfully remove a subscriber: %s for <Workitem %s>",
                      email, self)