We already skip the XI2 implementation, and the core one needs to the same treatment.
Since it can't be constructed without specifying a GdkWindow, which we don't have here.
Make sure that the tests don't access the host's session bus or installed gsettings schemas. Also disable tests for some classes that leak a connection to the session bus. https://bugzilla.gnome.org/show_bug.cgi?id=711715
