Comment 58 for bug 116870

Erm, just to add my $0,02, this warning has been displayed in all the glib development releases for a while and is hidden in stable release, hence the fact that one doesn't ever see it usually.
And for the record, it affects all pyGTK apps, and it's definitely not a problem most often, but a "stupidity" from glib developers (that's what I have been told by one of the pyGTK core developers).