Why Blender 2.49 does not show button on ubuntu like it does in windows? I have add-on for Blender 2.49b, python 2.6.6 and I need it to "show the button" to a user like this: 

result=Blender.Draw.PupMenu("Sketchfab Viewer ?%t|Yes|No")


But button does not show up in ubuntu, but it does in windows?

To run script press Alt+P in text windows and go in to addon folder than go in to 768dd88bd0bb49a8ad0a75ab143f685a and select astrea-768dd88bd0bb49a8ad0a75ab143f685a.html and hit Import. Then you should see



Edit: 
When I add print "2" on line 43 it does not show up in console so its problem in folder "newGameLib" I doubt that it contain some windows only releted command just like cls.

Also one thing should be changed line 3277 

os.system("cls") 


to

##os.system("cls")
You can find your addon for 2.79 and 2.8 in link here. 
https://github.com/sketchfab/blender-plugin 

If you are unfamiliar with 2.8, you can see basic tutorials in link below. 
https://www.youtube.com/playlist?list=PLa1F2ddGya_-UvuAqHAksYnB0qL9yWDO6 

Playlists of tutorials for 2.8x on page 4 and those for 2.7x on page 5. I regard those as best for absolute beginners. 
https://docs.google.com/presentation/d/13UpIjJEE7Oa7x5BiMsjXGW5CGOTDF03-SocRYi4Babs/