Need to handle no response condition

[djs]

PID may return NO DATA even when the car is running. Need to handle this condition

Traceback (most recent call last):
  File "backend.py", line 118, in <module>
    main()
  File "backend.py", line 108, in main
    record = poll(interface)
  File "backend.py", line 49, in poll
    intake_temp = interface.get_intake_air_temperature()
  File "/home/pi/obdii/obdii.py", line 130, in get_intake_air_temperature
    data = self._get_response([0x01, 0x0F])
  File "/home/pi/obdii/obdii.py", line 26, in _get_response
    response = self.adapter.send_obdii_command(command)
  File "/home/pi/obdii/elm.py", line 113, in send_obdii_command
    data.append(int(byte, 16))
ValueError: invalid literal for int() with base 16: 'NO'