Have lookup return None when it fails, moving the moving much of the try/except logic into single-line fallback expressions.

Make function private and don't use a different name for it, as it performs the same purpose. Also, it doesn't set anything.

Improve support for standalones MVC++ 9.0/10.0 compilers by setting directly the environment if Vcvarsall.bat is missing or fail.

setuptools no longer provides an upload command.