docs: def shutdown(self, signum):
          """Handle all signals which trigger a process stop.
  
          This method should run all appropriate signal handlers registered
          through the 'handle' method. At the end it should cause the process
          to exit with a status code. If any of the handlers raise an exception
          the exit code should be SHUTDOWN_FAILED otherwise SUCCESS.
          """
          dirty = False
          for handler in self._handlers[signum]:
  
              try:
  
                  handler()
  
              except:
  
                  LOG.exception("A shutdown handler failed to execute:")
                  dirty = True
  
          del self.pid
  
          if dirty:
  
              sys.exit(exit.SHUTDOWN_FAILED)
              return None
  
          sys.exit(exit.SUCCESS)
          return None