Ubuntu installer
Issue
https://bugs.launchpad.net/ubuntu/+source/debian-installer/+bug/1364906
https://launchpadlibrarian.net/178176319/ac100.diff
Ubuntu installer overview
Ubuntu and its various flavours (Kubuntu, Edubuntu, Xubuntu) have two installers. One is a modified version of the Debian installer, known as "d-i", and is written in POSIX shell script and C. The other, Ubiquity, is used on our live CD (or "desktop CD"), features a from-scratch user interface design, and has a good deal of front-end code written in Python, but behind the scenes still uses d-i code for many back-end tasks where it's important that we don't end up maintaining two implementations.
From installer development wiki article.
Links
http://bazaar.launchpad.net/~ubuntu-installer/ubiquity/trunk/annotate/head:/doc/README
http://d-i.alioth.debian.org/doc/internals/apa.html
https://wiki.ubuntu.com/Installer/Development
https://wiki.ubuntu.com/Installer/FAQ#How_do_I_debug_the_installer.3F