docs: def init_done(self, fut):
          """Server ready.
  
          If we get OSError during init the device is not available.
          """
          try:
              if fut.exception():
                  fut.result()
          except OSError as err:
              _LOGGER.debug('RTSP got exception %s', err)
              self.stop()
              self.callback(SIGNAL_FAILED)