Comment 5 for bug 1711735

The fix in bug 1679252 uses LB_PARENT_MIRROR_BINARY_SECURITY for security lines (where currently trusty uses LB_PARENT_MIRROR_BINARY; I don't _think_ this should work because LB_PARENT_MIRROR_BINARY is used for the other sources.list lines which are fine, but it's worth a try.

Commit with that change pushed up to https://code.launchpad.net/~daniel-thewatkins/ubuntu/+source/livecd-rootfs/+git/livecd-rootfs/+ref/bug/1711735, and I've kicked off a build of livecd-rootfs to attempt a build from.