Port python scripts to python3

[NoamDev]

Right now the automation uses python2 which deprecated. Ubuntu doesn't come with python2 anymore, you have to install python2.7 and then link /bin/python -> /bin/python2.7. I suggest to port the scripts to python3.

[NoamDev]

I'm willing to do it even myself if needed, @nigels-com do you think it'd be a good idea?

[nigels-com]

Yes, happy to consider a pull request.

[mariob92]

@NoamDev FYI: I started to rewrite the entire source generation scripts in Python 3 last year in https://github.com/nigels-com/glew/issues/318. It's still in an eraly state and I hadn't really time for progress since August.

[nigels-com]

My recollection is that the current scripts will work (or nearly) in Python 3 without too much refactoring. But providing they produce the same output as currently, don't mind a more extensive refactor. I do agree it's time (well past time, I guess) to default to Python 3.