Code review comment for lp:~phablet-team/media-hub/fix-1458040

> Feels a bit strange that we return "no_error" if there is an error. Should we
> not add a "unknown_error" to the Player error api?
> This seems likely to be the reason why this failed in the first place?

My limitation is the types of errors supported by QMediaPlayer: http://doc.qt.io/qt-5/qmediaplayer.html#Error-enum