Ubiquity eventually crashes after reverting encrypted partitions in the manual installer

[Jean-Baptiste Lallement]

Quantal Desktop 20120926

TEST CASE:
1. Start Ubiquity and go to the manual partitioner
2. Create a new partition: 500MB /boot ext4
3. Create a new partition: 16GB Physical volume for encryption
4. Press 'Revert'
5. Select the encrypted device and on this device
5.1. Create a new partition: 2GB swap area
5.2. Create a new partition: 14GB ext4 /
6. Continue with installation

ACTUAL RESULT:
This crash
Sep 26 09:52:56 ubuntu ubiquity[2830]: switched to page timezone
Sep 26 09:52:57 ubuntu partman: mke2fs 1.42.5 (29-Jul-2012)
Sep 26 09:52:59 ubuntu ubiquity: cat:
Sep 26 09:52:59 ubuntu ubiquity: 0-16675504127/mountpoint
Sep 26 09:52:59 ubuntu ubiquity: : No such file or directory
Sep 26 09:52:59 ubuntu ubiquity:
Sep 26 09:52:59 ubuntu kernel: [ 408.634734] EXT4-fs (sda1): mounted filesystem with ordered data mode. Opts: (null)
Sep 26 09:52:59 ubuntu ubiquity: cat:
Sep 26 09:52:59 ubuntu ubiquity: 0-16675504127/mountpoint
Sep 26 09:52:59 ubuntu ubiquity: : No such file or directory
Sep 26 09:52:59 ubuntu ubiquity:
Sep 26 09:53:00 ubuntu ubiquity[2830]: debconffilter_done: ubiquity.components.partman_commit (current: ubi-timezone)
Sep 26 09:53:00 ubuntu ubiquity: Traceback (most recent call last):
Sep 26 09:53:00 ubuntu ubiquity: File "/usr/share/ubiquity/install.py", line 693, in <module>
Sep 26 09:53:00 ubuntu ubiquity: install = Install()
Sep 26 09:53:00 ubuntu ubiquity: File "/usr/share/ubiquity/install.py", line 74, in __init__
Sep 26 09:53:00 ubuntu ubiquity: 'Failed to mount the target: %s' % str(self.target)
Sep 26 09:53:00 ubuntu ubiquity: AssertionError: Failed to mount the target: /target

ProblemType: Bug
DistroRelease: Ubuntu 12.10
Package: ubiquity 2.12.5
ProcVersionSignature: Ubuntu 3.5.0-15.23-generic 3.5.4
Uname: Linux 3.5.0-15-generic x86_64
ApportVersion: 2.5.2-0ubuntu4
Architecture: amd64
CasperVersion: 1.324
Date: Wed Sep 26 11:53:03 2012
InstallCmdLine: file=/cdrom/preseed/ubuntu.seed boot=casper initrd=/casper/initrd.lz quiet splash -- maybe-ubiquity
LiveMediaBuild: Ubuntu 12.10 "Quantal Quetzal" - Beta amd64 (20120926)
ProcEnviron:
 TERM=linux
 PATH=(custom, no user)
 LANG=en_US.UTF-8
SourcePackage: ubiquity
UpgradeStatus: No upgrade log present (probably fresh install)

[Ubuntu QA Website (ubuntuqa)]

This bug has been reported on the Ubuntu ISO testing tracker.

A list of all reports related to this bug can be found here:
http://iso.qa.ubuntu.com/qatracker/reports/bugs/1056744

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Dimitri John Ledkov (xnox)]

The Revert button (ubiquity UI) or "Undo changes" (debian-installer UI) do not recursively remove create device mapper nodes created with partman-crypto configure or activate menu items. LVM is not affected as much, as one can manually remove volume groups using the lvm menu. Further checking is needed what happens with partman-md during undo.