XXX_NICK_XXX not substituted on Wheezy

Originally created by @intrigeri on #6273 (Redmine)

/var/log/live/config.log reads:

 resolv-conf debconf hostname user-setup locales-all tzdata keyboard-configuration sysvinit sysv-rc gnome-panel-data gnome-power-manager kde-services util-linux login xserver-xorgupdate-alternatives: error: alternative /usr/bin/gnome-session for x-session-manager not registered; not setting
:ERROR

So apparently all hooks that follow (including our own 2010-pidgin and others) are not run.

Parent Task: #6015 (closed)