Comment 3 for bug 1739790

Thank you for your bug report.

Indeed it's obvious from the code was is wrong and should be trivial to fix

functions/defaults.sh has that code

' ubuntu)
   LB_SYSLINUX_THEME="${LB_SYSLINUX_THEME:-ubuntu-oneiric}"
   ;;'

Or the -oneiric binary got removed in xenial so it's probably a matter for doing s/oneiric/xenial there

Tagging rls for foundations review they know better the image build tools and what modes are supposed in Ubuntu