Comment 2 for bug 1172851

This is _not_ plainbox specific, tested on raring, with plainbox 0.2+bzr2082+bzr10~raring1 and checkbox 0.15.5

zyga@purple:~$ sudo /usr/share/checkbox/scripts/gpu_test
/bin/sh: 1: wmctrl: not found
Traceback (most recent call last):
  File "/usr/share/checkbox/scripts/gpu_test", line 204, in <module>
    sys.exit(main())
  File "/usr/share/checkbox/scripts/gpu_test", line 162, in main
    shell=True)
  File "/usr/lib/python3.3/subprocess.py", line 586, in check_output
    raise CalledProcessError(retcode, process.args, output=output)
subprocess.CalledProcessError: Command 'wmctrl -l | grep glxgears' returned non-zero exit status 1