Automatic-ubiquity installation of Lucid desktop with preseed ignores/clobbers preseeded values when creating /etc/apt/sources.list

Binary package hint: ubiquity

I realize these are "older" versions of the software, this problem doesn't seem to affect either Maverick or Natty, however I am reporting this as we are still conducting tests with Lucid and this issue gives us some problems when trying to install openssh-server, due to the incorrect sources.list.

Steps to reproduce:
1- Remaster a CD image with ubuntu-10.04.2-desktop-i386.iso, using the attached ubuntu.seed file instead of the one provided in the CD (the relevant part are all the d-i mirror/* settings, the rest is just for completeness).
2- Boot with the CD, press a key, move to "install ubuntu" and press F6
3- replace "only-ubiquity" with "automatic-ubiquity" and press enter install using the preseed file's data.

Expected result:
/etc/apt/sources.list pointing to our local mirror, and containing lines of the form:

deb http://10.153.104.60//rsync.releases.ubuntu.com/releases/lucid/ubuntu-10.04.2-server-i386 lucid main restricted

as per the preseed file's configuration:

d-i mirror/country string manual
d-i mirror/http/hostname string 10.153.104.60
d-i mirror/http/directory string //rsync.releases.ubuntu.com/releases/lucid/ubuntu-10.04.2-desktop-i386
d-i mirror/http/proxy string
d-i mirror/http/mirror string 10.153.104.60

Actual result:

mirror/http/mirror gets replaced with a mirror according to the country as specified by debian-installer/locale. For instance, if locale is es_ES, we get lines of the form:

deb http://es.archive.ubuntu.com//rsync.releases.ubuntu.com/releases/lucid/ubuntu-10.04.2-desktop-i386 lucid main restricted

I tested setting

d-i mirror/http/mirror string ch.archive.ubuntu.com

and it still gets overwritten with es.archive.ubuntu.com.

This does not happen with either the alternate or server editions, both using plain debian-installer; it only happens under Ubiquity.

I'm attaching the test preseed file, as well as ubiquity's debug file, obtained using debug-ubiquity on an actual test system.

ProblemType: Bug
DistroRelease: Ubuntu 10.04
Package: ubiquity 2.2.25
ProcVersionSignature: Ubuntu 2.6.32-28.55-generic 2.6.32.27+drm33.12
Uname: Linux 2.6.32-28-generic i686
Architecture: i386
Date: Wed Mar 9 19:52:47 2011
LiveMediaBuild: Ubuntu 10.04.2 LTS "Lucid Lynx" - Release i386 (20110211.1)
ProcEnviron:
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: ubiquity