docs: def stopCommand(self):
          """Make any currently-running command die, with no further status
          output. This is used when the worker is shutting down or the
          connection to the master has been lost. Interrupt the command,
          silence it, and then forget about it."""
          if not self.command:
              return
          log.msg("stopCommand: halting current command {0}".format(self.command))
          self.command.doInterrupt()  # shut up! and die!
          self.command = None