[bigretromike]

@Roman_V_M your are a professional python developer, for you It could looked weird.

Sorry for not being clear. The error itself looks weird, not your code (except for self in super). Explicit call to xbmcgui.WindowXML.__init__(self, xml_file, resource_path, skin, skin_res, False) should work.

@rmrector New-style classes (in Python 3 you have only them) must accept arguments in super() call if the respective parent class' method accept those arguments. It looks like a bug/feature in C++/Python wrapper used in Kodi where wrapped classes exposed to Python have their own type rather than being instances of the standard type. 

Thats what I read for most parts, that It should worked - but then again it didn't. Yet removing it fix issue and both version py2 and py3 work flawless, so I don't really know :-) but I'm happy that my project work on both versions now.