Comment 8 for bug 1557752

IRC comment from ximion

"libappstream does that by default, check /etc/appstream.conf
maybe hughsie dropped that from appstream-glib
the main problem is that we don't know if a screenshot on screenshots.d.o actually exists
 so with libappstream, people will get a filler image in that case
 maybe that wasn't wanted
 implementing support for this in GS or as-glib should be rather simple though"