docs: def gracefulShutdown(self):
          """Start shutting down"""
          if not self.bf.perspective:
              log.msg("No active connection, shutting down NOW")
              reactor.stop()
              return
  
          log.msg(
              "Telling the master we want to shutdown after any running builds are finished")
          d = self.bf.perspective.callRemote("shutdown")
  
          def _shutdownfailed(err):
              if err.check(AttributeError):
                  log.msg(
                      "Master does not support worker initiated shutdown.  Upgrade master to 0.8.3 or later to use this feature.")
              else:
                  log.msg('callRemote("shutdown") failed')
                  log.err(err)
  
          d.addErrback(_shutdownfailed)
          return d