Code review comment for lp:~carla-sella/music-app/add_song_and_play

Sometimes this will fail on my device;

<balloons> Traceback (most recent call last):
<balloons> File "/home/phablet/autopilot/music_app/tests/test_music.py", line 465, in test_create_playlist_from_songs_tab
<balloons> self.assertThat(playlist, Not(Is(None)))
<balloons> File "/usr/lib/python2.7/dist-packages/testtools/testcase.py", line 412, in assertThat
<balloons> raise MismatchError(matchee, matcher, mismatch, verbose)
<balloons> MismatchError: None matches Is(None)