docs: def cleanup():
      """Stop all started tasks on system exit.
  
      Note: This only handles signals caught by the atexit module by default.
      SIGKILL, for instance, will not be caught, so cleanup is not guaranteed in
      all cases.
      """
      to_stop = STARTED_TASKS.copy()
      if to_stop:
          print "Cleaning up..."
      for task in to_stop:
          try:
              task.stop()
          except: # pylint: disable=W0702
              etype, value, trace = sys.exc_info()
              # Disregard no such process exceptions, print out the rest
              if not (isinstance(value, OSError) and value.errno == 3):
                  print ''.join(format_exception(etype, value, trace, None))
              continue