def _get_last_worker_died(self):
        """Return the last died worker information or None"""
        for service_id in list(self._running_services.keys()):
            # We copy the list to clean the orignal one
            processes = list(self._running_services[service_id].items())
            for process, worker_id in processes:
                if not process.is_alive():
                    self._run_hooks('dead_worker', service_id, worker_id,
                                    process.exitcode)
                    if process.exitcode < 0:
                        sig = _utils.signal_to_name(process.exitcode)
                        LOG.info('Child %(pid)d killed by signal %(sig)s',
                                 dict(pid=process.pid, sig=sig))
                    else:
                        LOG.info('Child %(pid)d exited with status %(code)d',
                                 dict(pid=process.pid, code=process.exitcode))
                    del self._running_services[service_id][process]
                    return service_id, worker_id
Return the last died worker information or None