As explained in bug 425156, gksu is dead and should be replaced by direct polkit usage when needed (as was done with gparted). Thanks
I suppose we can remove both gksu and kdesu usage and just use pkexec everywhere instead?
Yes, that is also possible :), I talked about gksu because its upstream is deprecating it for a long time, but no idea about kdesu
Fixed in -r1, which will be stabilized soon.
Thanks Davide!