Comment 3 for bug 1325281

This is happening because linux-signed-generic is in the live task, which I should have realised was invalid: that expands to ABI-versioned kernel packages, and tasks can't be updated post-release.

I've fixed this in utopic (for future stable releases) by making livecd-rootfs 2.218 install linux-signed-generic explicitly, and removing it from the seeds. However, we'll need a slightly different fix for trusty since we can't change the existing tasks: livecd-rootfs will need to filter out kernel packages from the live seed, as well as installing linux-signed-generic explicitly as in utopic.