Audio playback tests fail due to permissions issue

Here's complete output from one of the tests (playback_hdmi):

INFO:===========================[ Saving audio settings ]============================ ERROR:Failed to save active profiles information: [Errno 13] Permission denied: 'active_profiles' ERROR:No available port found ERROR:Failed to find status for device: hdmi Attempting to initialize Gstreamer pipeline: audiotestsrc wave=sine freq=512 ! audioconvert ! audioresample ! autoaudiosink Pipeline initialized, now starting playback. INFO:==========================[ Restoring audio settings ]==========================

Interestingly, this failure comes from checkbox_support, where the bulk of the audio_settings.py script lives.

there are two places in that script where we do stuff like open('active_profiles'), but the PWD for the script is root (/), so when running as a normal user it has no permissions, thus causing the mentioned error.

This script is the only place where we use this active_profiles file, possible fixes include referring this to $PLAINBOX_SESSION_DATA (which I'd prefer to avoid) or setting it to a known location in a temporary directory (/tmp/ somewhere). I'm not yet clear if two different invocations of audio_settings will need access to this file; I think not, and that's what the --file parameter is for (persistent settings storage), but I'll read the code more closely to see if we need something persistent or whether maybe a temporary file (mktemp) would do.