def set_signals():
    """Set up the signal handlers necessary to control the runner.

        The runner should catch the following signals:
        - SIGTERM and SIGINT: treated exactly the same, they cause the runner
          to exit with no restart from the master.
        - SIGUSR1: Also causes the runner to exit, but the master watcher will
          retart it.
        - SIGHUP: Re-open the log files.
        """
