Comment 1 for bug 2008931

Changing :

    def _get_updated_comment(self, vol_name, **values):
        vol = self.client.getVolume(vol_name)
        comment = json.loads(vol['comment']) if vol['comment'] else {}
        comment.update(values)

to

    def _get_updated_comment(self, vol_name, **values):
        vol = self.client.getVolume(vol_name)
        comment = json.loads(vol['comment']) if vol.get('comment') else {}
        comment.update(values)

resolves the issue.