ValueError: Namespace Gdk not available

$ bcloud-gui 
Traceback (most recent call last):
  File "/usr/bin/bcloud-gui", line 11, in <module>
    from bcloud.App import App
  File "/usr/lib64/python3.5/site-packages/bcloud/App.py", line 12, in <module>
    gi.require_version('Gdk', '3.0')
  File "/usr/lib64/python3.5/site-packages/gi/__init__.py", line 102, in require_version
    raise ValueError('Namespace %s not available' % namespace)
ValueError: Namespace Gdk not available