Use Gtk.Widget Method instead of Gtk.Button for set_focus_on_click

Gtk.Button.set_focus_on_click was deprecated in GTK 3.2, and replaced by Gtk.Widget.set_focus_on_click. Gtk.Button inherits from Gtk.Widget, but if you call Gtk.Button.set_focus_on_click it introspects to gtk_button_set_focus_on_click instead of gtk_widget_set_focus_on_click.

What this results in for a simple example is:

button = Gtk.Button()
button.set_focus_on_click(False)
DeprecationWarning: Gtk.Button.set_focus_on_click is deprecated
    button.set_focus_on_click(False)

You can work around this by directly calling the Gtk.Widget method like:

button = Gtk.Button()
Gtk.Widget.set_focus_on_click(button, False)

Could we modify PyGObject so that it doesn't call the deprecated method at all?