"update-manager --devel-release": Upgrade button does nothing, even after successful authentication

Steps to reproduce (on Quantal):

1. Press Alt+F2 and type "update-manager --devel-release"
2. If any packages are out-of-date, update them first
3. When prompted that Ubuntu 13.04 (Raring) is available, click "Upgrade"
4. Type your password at the authentication prompt, and click "Authenticate"

Expected result: A release upgrade dialog should appear

What happens instead: Nothing.

Workaround:

$ sudo su
# echo "deb http://us.archive.ubuntu.com/ubuntu raring main restricted universe multiverse" > /etc/apt/sources.list
# echo "deb http://us.archive.ubuntu.com/ubuntu raring-security main restricted universe multiverse" >> /etc/apt/sources.list
# echo "deb http://us.archive.ubuntu.com/ubuntu raring-updates main restricted universe multiverse" >> /etc/apt/sources.list
# echo "deb http://us.archive.ubuntu.com/ubuntu raring-proposed main restricted universe multiverse" >> /etc/apt/sources.list
# echo "deb http://us.archive.ubuntu.com/ubuntu raring-backports main restricted universe multiverse" >> /etc/apt/sources.list
# apt-get update && apt-get -y dist-upgrade
# exit

ProblemType: Bug
DistroRelease: Ubuntu 12.10
Package: update-manager 1:0.174.3
Uname: Linux 3.4.0 x86_64
ApportVersion: 2.6.1-0ubuntu9
Architecture: amd64
Date: Thu Jan 10 08:24:50 2013
GsettingsChanges:
 b'com.ubuntu.update-manager' b'first-run' b'false'
 b'com.ubuntu.update-manager' b'launch-time' b'1357834984'
 b'com.ubuntu.update-manager' b'show-details' b'true'
 b'com.ubuntu.update-manager' b'window-height' b'240'
 b'com.ubuntu.update-manager' b'window-width' b'640'
InstallationDate: Installed on 2012-04-26 (259 days ago)
InstallationMedia: Ubuntu 12.04 LTS "Precise Pangolin" - Release amd64 (20120425)
MarkForUpload: True
PackageArchitecture: all
ProcEnviron:
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: update-manager
UpgradeStatus: Upgraded to quantal on 2013-01-07 (2 days ago)