[Merge] lp:~rcj/livecd-rootfs/trunk into lp:livecd-rootfs

[Robert C Jennings]

I've tested these new changes and it works well.  Doesn't break downstream cloud images.  And it will allow subsequent hooks to overwrite non-generic assertions.  Please review.
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https://code.launchpad.net/~rcj/livecd-rootfs/trunk/+merge/355791
Your team Ubuntu Core Development Team is requested to review the proposed merge of lp:~rcj/livecd-rootfs/trunk into lp:livecd-rootfs.