make it compatible with Python3, remove -Werror

[matthiasdiener]

Fixes #34.

[baryluk]

Why you need to use 2to3 at runtime and not change all problematic places once and commit this to repo?

[matthiasdiener]

Why you need to use 2to3 at runtime and not change all problematic places once and commit this to repo?

Because CXL_init.py (the only file handled by 2to3) is not actually contained within this repo (it is a symlink to ../Common/Src/Scons), but is located in a read-only, archived repo (https://github.com/GPUOpen-Archive/common-src-SCons), and I therefore can't open Pull Requests that modify this file anymore.