Start a packet capture in uBridge.

        :param adapter_number: adapter number
        :param output_file: PCAP destination file for the capture

def _start_ubridge_capture(self, adapter_number, output_file):
        """
        Start a packet capture in uBridge.

        :param adapter_number: adapter number
        :param output_file: PCAP destination file for the capture
        """

        adapter = "bridge{}".format(adapter_number)
        if not self.ubridge:
            raise DockerError("Cannot start the packet capture: uBridge is not running")
        yield from self._ubridge_send('bridge start_capture {name} "{output_file}"'.format(name=adapter, output_file=output_file))