(originally reported against Fedora: https://bugzilla.redhat.com/show_bug.cgi?id=960149)

Trying to unlock Gnome in a remote ThinLinc session results in "Authentication error" and a never ending spinner. This is what the log has to say:

    JS ERROR: !!!   Failed to open reauthentication channel
    JS ERROR: !!!     message = '"GDBus.Error:org.gtk.GDBus.UnmappedGError.Quark._gdm_5fdisplay_5ferror.Code2: Error getting seat id from systemd: No such file or directory"'
    JS ERROR: !!!     fileName = 'undefined'
    JS ERROR: !!!     lineNumber = 'undefined'
    JS ERROR: !!!     stack = 'undefined'
    JS ERROR: !!!   Exception was: TypeError: this._userVerifier is undefined
    JS ERROR: !!!     message = '"this._userVerifier is undefined"'
    JS ERROR: !!!     fileName = '"/usr/share/gnome-shell/js/gdm/util.js"'
    JS ERROR: !!!     lineNumber = '456'
    JS ERROR: !!!     stack = '"(false)@/usr/share/gnome-shell/js/gdm/util.js:456
wrapper(false)@/usr/share/gjs-1.0/lang.js:213
("Failed to open reauthentication channel",[object GObject_Boxed])@/usr/share/gnome-shell/js/gdm/util.js:250
wrapper("Failed to open reauthentication channel",[object GObject_Boxed])@/usr/share/gjs-1.0/lang.js:213
([object GObject_Object],[object GObject_Object])@/usr/share/gnome-shell/js/gdm/util.js:266
wrapper([object GObject_Object],[object GObject_Object])@/usr/share/gjs-1.0/lang.js:213
"'

Since this is a remote session, a lack of a seat is perfectly normal.

Similar behaviour has been noticed on Fedora 18, but the log there is more unclear:

    JS ERROR: !!!   Exception was: TypeError: Object 0x7fee89e73e18 is not a subclass of (null), it's a GLib_Error
    JS ERROR: !!!     message = '"Object 0x7fee89e73e18 is not a subclass of (null), it's a GLib_Error"'
    JS ERROR: !!!     fileName = '"/usr/share/gnome-shell/js/gdm/util.js"'
    JS ERROR: !!!     lineNumber = '159'
    JS ERROR: !!!     stack = '"([object _private_Gdm_Client],[object _private_Gio_SimpleAsyncResult])@/usr/share/gnome-shell/js/gdm/util.js:159
wrapper([object _private_Gdm_Client],[object _private_Gio_SimpleAsyncResult])@/usr/share/gjs-1.0/lang.js:204
"'


If the lock screen relies on GDM for PAM access, it really shouldn't start at all if it isn't launched from GDM.