Python 3 compatibility

I saw the post from the guy having an issue with running it with python 3, so as it is a simple python file, I managed to make the compatibility between the python 2 and 3.
This was quite easy as it mostly the print instruction which has been modified in python 3 to be a print function. Fortunately we can use the "from __future__ import" statement :-)
The other problem that it can face it Gtk3. Gtk3 is not pygtk anymore and is using GI imports. I wrapped that to make it work too just in case.