Comment 12 for bug 478274

Digging somewhat more, it appears that none of the seats allow to activate sessions (CanActivateSession) except one. The strange thing is that that one seat doesn't contain any session. The other strange thing is that none of the seats are associated with any device (GetDevices).

Anyway, here is what a slightly more complete version of the script above tells me in a graphical session:
-----------------------------------------------------------------------------
# Seat '/org/freedesktop/ConsoleKit/Seat2':
  can_activate: 1
  devices: dbus.Array([], signature=dbus.Signature('(ss)'))
  active_session: None
# Seat '/org/freedesktop/ConsoleKit/Seat14':
  can_activate: 0
  devices: dbus.Array([], signature=dbus.Signature('(ss)'))
  active_session: None
  # Session '/org/freedesktop/ConsoleKit/Session12':
Traceback (most recent call last):
  File "./x.py", line 25, in <module>
    session.Activate()
  File "/usr/lib/pymodules/python2.6/dbus/proxies.py", line 140, in __call__
    **keywords)
  File "/usr/lib/pymodules/python2.6/dbus/connection.py", line 620, in call_blocking
    message, timeout)
DBusException: org.freedesktop.DBus.GLib.UnmappedError.CkSeatError.Code0: Activation is not supported for this kind of seat
-----------------------------------------------------------------------------

One last strange thing... When I log out from my graphical session and type ck-list-sessions in a console terminal, I can notice that gdm has a session of its own, but that session is not active either and, in fact, none of the sessions is marked as 'active', even my console session:
-----------------------------------------------------------------------------
Session16:
 unix-user = '1000'
 realname = 'david'
 seat = 'Seat18'
 session-type = ''
 active = FALSE
 x11-display = ''
 x11-display-device = ''
 display-device = '/dev/tty1'
 remote-host-name = ''
 is-local = TRUE
 on-since = '2009-11-14T15:38:16.887770Z'
 login-session-id = '4294967295'
Session13:
 unix-user = '105'
 realname = 'Gnome Display Manager'
 seat = 'Seat15'
 session-type = 'LoginWindow'
 active = FALSE
 x11-display = ':0'
 x11-display-device = '/dev/tty7'
 display-device = ''
 remote-host-name = ''
 is-local = TRUE
 on-since = '2009-11-14T15:37:34.131625Z'
 login-session-id = '4294967295'
-----------------------------------------------------------------------------
Would anybody have any clue for that ?