import gi
gi.require_version("Gtk", "3.0")
from gi.repository import Gtk

window = Gtk.Window(title="Hello World")
window.show()
window.connect("destroy", Gtk.main_quit)
Gtk.main()

from gi.repository import Gtk

from gi.overrides import Gtk

Traceback (most recent call last):
  File "/Users/alberto/PycharmProjects/p1-ipm-16-17-Otloal/main.py", line 2, in <module>
    gi.require_version("Gtk", "3.0")
  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/gi/__init__.py", line 127, in require_version
    raise ValueError('Namespace %s not available' % namespace)
ValueError: Namespace Gtk not available

brew reinstall gtk+3 pygobject3