See https://bugzilla.redhat.com/show_bug.cgi?id=809213
https://bugzilla.redhat.com/show_bug.cgi?id=810052#c8

Apparently, creating a GDBus proxy for ConsoleKit causes GDBus automatically to try and list properties, but ConsoleKit is configured in its installed policy to reject that. This produces messages in /var/log/messages:

Apr  1 14:27:54 jik2 dbus-daemon[834]: dbus[834]: [system] Rejected send message, 2 matched rules;  type="method_call", sender=":1.112" (uid=3009 pid=3770 comm="/usr/bin/gnome-shell ") interface="org.freedesktop.DBus.Properties" member="GetAll" error name="(unset)" requested_reply="0" destination=":1.19" (uid=0 pid=2316 comm="/usr/sbin/console-kit-daemon --no-daemon ")

Using  G_DBUS_PROXY_FLAGS_DO_NOT_LOAD_PROPERTIES when creating the proxy would fix this, but there's no way to wedge that into:
 
 const ConsoleKitSessionProxy = Gio.DBusProxy.makeProxyWrapper(ConsoleKitSessionIface);

Using new Gio.DBusProxy as is done a couple of places in the shell would allow fixing this, but it seems like there should be a way to pass flags when using the convenience form, since the full form is pretty ugly.

(So perhaps we should uglify things in the gnome-3-4 branch but do something better with a GJS API addition for the master branch.)