When I run applications like Synaptic or Gparted, I'm prompted by the lovely screen on the left, to enter my admin password. I think this has something to do with pkexec.
But when I run applications using gksu I am prompted by the ugly window on the right.
I'd like to run Nautilus or Gedit sometimes as root and be prompted by the nicer window on the left.
Update 2015/4/09 6:00pm
$ pkexec gedit
gdk_mir_display_open
Failed to connect to Mir: Failed to connect to server socket: No such file or directory
Unable to init server: Could not connect: Connection refused
(gedit:9664): Gtk-WARNING **: cannot open display:
