Comment 4 for bug 1717451

Thanks for spineau's comment. The default job comment use /dev/external_webcam which comes form checkbox-satellite preseed.

The preseed comes from checkbox-message hardcoded configuration as a part of the initial input parameters. In checkbox-message it is hardcoded two webcam models.

Conclusion:
If the system is not provisioned by checkbox-satellite, it wont has /dev/external_webcam. So this opencv test will failed.