Esri/portalpy — pull request #5 by WestonSF (2014-04-03 08:26:18+00:00)
Title: Change to add_group_users function as didn't seem to work.

Changed:
user_names = _unpack(user_names, 'username')
postdata = self._postdata()
postdata['users'] = ','.join(user_names)

To:
postdata = self._postdata()
postdata['users'] = user_names