gi.require_version('Gdk', '3.0')
  File "/nix/store/9spzr078zk13sj0by1nil650jnbs60kc-python3.6-pygobject-3.24.1/lib/python3.6/site-packages/gi/__init__.py", line 118, in require_version
    raise ValueError('Namespace %s not available' % namespace)
ValueError: Namespace Gdk not available