musicbrainz/picard — pull request #91 by zas (2013-01-28 14:10:28+00:00)
Title: Request CAA only if MB indicates release has caa artwork

Since 2013/01/28, web service is indicating if release has artwork
at cover art archive, use this info to prevent useless requests.
Related to http://tickets.musicbrainz.org/browse/MBS-4536