[Bug 95167] "Start New Session" from Gnome doesn't work when kdm is the default display manager

[PeteDonnell]

Public bug reported:

Apologies if this is a dupe, I was unable to find a previous version of
it.

Steps to reproduce:
Install ubuntu-desktop and kubuntu-desktop.
Choose kdm as the default login manager.
Log in to a Gnome session.
Select "Start New Session" from Gnome menu.
New session fails to start.

However, if you log in to a KDE session, the Switch User/Start New
Session works fine, even if you want to log in to Gnome on the second
session. There is particularly a problem if someone has started a Gnome
session, then gone away and locked the computer. In KDE this isn't a
problem as a subsequent user can just start a new session and use their
own login. Presumably switching to a terminal via Ctrl-Alt-Fx and
launching a new session by hand would work, although I haven't tested
it, but that's way beyond the tech level of most of the users of the
computer I have where this is a problem.

I realise this may well be a problem with Gnome and kdm not working well
together, independent of Ubuntu.

** Affects: gdm (Ubuntu)
     Importance: Undecided
         Status: Unconfirmed

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"Start New Session" from Gnome doesn't work when kdm is the default display manager
https://launchpad.net/bugs/95167