'Called when reciving the :const:`WORKER_UP` message.
Marks the process as ready to receive work.'

def on_process_alive(self, pid):

    try:
        proc = next((w for w in self._pool if (w.pid == pid)))
    except StopIteration:
        return logger.warning(u'process    with    pid=%s    already    exited', pid)
    assert (proc.inqW_fd not in self._fileno_to_inq)
    assert (proc.inqW_fd not in self._all_inqueues)
    self._waiting_to_start.discard(proc)
    self._fileno_to_inq[proc.inqW_fd] = proc
    self._fileno_to_synq[proc.synqW_fd] = proc
    self._all_inqueues.add(proc.inqW_fd)
