Manages a daemonized crawler thread.

        Once a crawler it finished, it loads the next one.

def manage_daemon(self):
        """
        Manages a daemonized crawler thread.

        Once a crawler it finished, it loads the next one.
        """
        while not self.shutdown:
            # next scheduled daemon, tuple (time, index)
            item = self.daemon_list.get_next_item()
            cur = time.time()
            pajama_time = item[0] - cur
            if pajama_time > 0:
                self.thread_event.wait(pajama_time)
            if not self.shutdown:
                self.start_crawler(item[1], daemonize=True)