Comment 3 for bug 1463583

Sources.gz (not .tar.gz) downloaded from archive.ubuntu.com/ubuntu/ubuntu/ubuntu/dists/vivid/main/source/Sources.gz does NOT contain gfxboot-theme-ubuntu*

So, a workaround would be to patch the /usr/lib/uck/customization-profiles/localized_cd/customize_iso script to check to make sure gfxboot-theme-ubuntu exists in Sources.gz

If it doesn't exist, then set GFXBOOT_THEME_UBUNTU_SOURCE_PACKAGE=gfxboot-theme-ubuntu_0.16.1.tar.gz. (The uck script expects tar.gz, not tar.xz)

This is what worked for me.

Additonally, if working in Ubuntu 15.04, you will also need to path the /usr/lib/uck/remaster-live-cd.sh script to "echo" error messages when isohybrid does not exist:

failure "You asked for a hybrid ISO but isohybrid command was not found" -> echo "You asked for a hybrid ISO but isohybrid command was not found"