docs: def evaluate_stop_condition(errdata, stop_condition):
      """
      Call the user-defined function: stop_condition(errdata)
      If the function returns -1, do nothing.  Otherwise, sys.exit.
      """
      if stop_condition:
          return_code = stop_condition(list(errdata))
          if return_code != -1:
              log.info(
                  'Stop condition triggered!  Relay is terminating.',
                  extra=dict(return_code=return_code))
              sys.exit(return_code)