code: def respond_to_SIGHUP(signal_number, frame, logger=None):
      
      global restart
      restart = True
      if logger:
          logger.info('detected SIGHUP')
      raise KeyboardInterrupt
docs: raise the KeyboardInterrupt which will cause the app to effectively
      shutdown, closing all it resources.  Then, because it sets 'restart' to
      True, the app will reread all the configuration information, rebuild all
      of its structures and resources and start running again