In a normal python program, Ctrl-C will set up a KeyboardInterrupt and terminate the program. This works with a normal python script, including GTK2 gtk.main(), but GTK3 Gtk.main() (even when used in a more robust GTK program than coded below) will not terminate with Ctrl-C requiring a Ctrl-Z and killing the job to terminate. See the commmand line output below:

$ python -c "while True:
>  pass
> "
^CTraceback (most recent call last):

+ Trace 229756

$ python -c "from gi.repository import Gtk
> Gtk.main()
> "
^C
^C
^Z
[1]+  Stopped                 python -c "from gi.repository import Gtk
Gtk.main()
"
$ kill %1

[1]+  Stopped                 python -c "from gi.repository import Gtk
Gtk.main()
"

The behaviour under Gtk.main() should be changed to respond to the KeyboardInterrupt.