launching xkill

[Megh Parikh <meghjp gmail com>]

 the following code deoes not run (it shows hello but the x arrow does not come)

gedit using the same code works. why??

button.connect('button-press-event',  Lang.bind(this, function () {
    if (GLib.spawn_command_line_sync('xkill')) _showHello();
        }));