[Merge] ~dbungert/livecd-rootfs:lp-2031027-canary-lang-layers into livecd-rootfs:ubuntu/master

[Steve Langasek]

LGTM though I wonder if the catalog changes should be handled separately; see inline comment
-- 
https://code.launchpad.net/~dbungert/livecd-rootfs/+git/livecd-rootfs/+merge/449215
Your team Ubuntu Core Development Team is requested to review the proposed merge of ~dbungert/livecd-rootfs:lp-2031027-canary-lang-layers into livecd-rootfs:ubuntu/master.