Cannot start VPN plugin authentication dialogs

[Mathieu Trudel-Lapierre]

All NetworkManager VPN plugins fail to start with an error in keyfile load_from_data():

    JS ERROR: !!! error while reading VPN plugin output keyfile
    JS ERROR: !!! message = '"Cannot convert string to array of 'utf8'"'
    JS ERROR: !!! fileName = '"/usr/share/gnome-shell/js/ui/networkAgent.js"'
    JS ERROR: !!! lineNumber = '538'
    JS ERROR: !!! stack = '"()@/usr/share/gnome-shell/js/ui/networkAgent.js:538
wrapper()@/usr/share/gjs-1.0/lang.js:204
([object _private_Gio_DataInputStream],[object _private_Gio_SimpleAsyncResult])@/usr/share/gnome-shell/js/ui/networkAgent.js:517
"'

I started debugging this bug couldn't get much farther than noting the issue is with taking the string data in load_from_data(). Here is some example data from a VPN plugin, which fails to be parsed. The same applies if Gnome Shell is started with LC_ALL=C, and all the data passed from the plugins is in English:

      JS LOG: Data from plugin:
[VPN Plugin UI]
Version=2
Description=Vous devez vous authentifier pour accéder au réseau privé virtuel « Connexion VPN 1 ».
Title=Authentifier le VPN

[Xauth password]
Value=
Label=Mot de passe :
IsSecret=true
ShouldAsk=true

[IPSec secret]
Value=
Label=Mot de passe du groupe :
IsSecret=true
ShouldAsk=true

      JS LOG: Data length: 318

ProblemType: Bug
DistroRelease: Ubuntu 12.10
Package: gnome-shell 3.5.4-0ubuntu2
ProcVersionSignature: Ubuntu 3.5.0-10.10-generic 3.5.1
Uname: Linux 3.5.0-10-generic x86_64
NonfreeKernelModules: nvidia
ApportVersion: 2.4-0ubuntu6
Architecture: amd64
Date: Wed Aug 15 09:47:03 2012
InstallationMedia: Ubuntu 12.10 "Quantal Quetzal" - Alpha amd64 (20120702)
ProcEnviron:
 LANGUAGE=fr_CA:fr
 TERM=xterm
 PATH=(custom, user)
 LANG=fr_CA.UTF-8
 SHELL=/bin/zsh
SourcePackage: gnome-shell
UpgradeStatus: No upgrade log present (probably fresh install)

[Daniel van Vugt (vanvugt)]

Thank you for reporting this bug to Ubuntu.
Ubuntu 12.10 (quantal) reached end-of-life on May 16, 2014.

See this document for currently supported Ubuntu releases:
https://wiki.ubuntu.com/Releases

We appreciate that this bug may be old and you might not be interested in discussing it any more. But if you are then please upgrade to the latest Ubuntu version and re-test.

[Launchpad Janitor (janitor)]

[Expired for gnome-shell (Ubuntu) because there has been no activity for 60 days.]