Instructions for installing the patches to test (in Matthias' comment https://bugs.launchpad.net/ubuntu/+source/appstream/+bug/1579712/comments/24 on bug #1579712) *did* solve the issue for me.
Instructions for installing the patches to test (in Matthias' comment https:/ /bugs.launchpad .net/ubuntu/ +source/ appstream/ +bug/1579712/ comments/ 24 on bug #1579712) *did* solve the issue for me.