Start an auxilary console

def _start_aux(self):
        """
        Start an auxilary console
        """

        # We can not use the API because docker doesn't expose a websocket api for exec
        # https://github.com/GNS3/gns3-gui/issues/1039
        process = yield from asyncio.subprocess.create_subprocess_exec(
            "docker", "exec", "-i", self._cid, "/gns3/bin/busybox", "script", "-qfc", "while true; do TERM=vt100 /gns3/bin/busybox sh; done", "/dev/null",
            stdout=asyncio.subprocess.PIPE,
            stderr=asyncio.subprocess.STDOUT,
            stdin=asyncio.subprocess.PIPE)
        server = AsyncioTelnetServer(reader=process.stdout, writer=process.stdin, binary=True, echo=True)
        self._telnet_servers.append((yield from asyncio.start_server(server.run, self._manager.port_manager.console_host, self.aux)))
        log.debug("Docker container '%s' started listen for auxilary telnet on %d", self.name, self.aux)