<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def mark_in_progress(self, rr_id: str, rr_size: int) -> None: """ Prepare sentinel directory for revocation registry construction. :param rr_id: revocation registry identifier :rr_size: size of revocation registry to build """

        try:
            makedirs(join(self._dir_tails_sentinel, rr_id), exist_ok=False)
        except FileExistsError:
            LOGGER.warning('Rev reg %s construction already in progress', rr_id)
        else:
            open(join(self._dir_tails_sentinel, rr_id, '.{}'.format(rr_size)), 'w').close()