-1 on that patch. It's using trickery to implement the test, and it's not clear that it is actually as efficient as the previous version. The previous version was explicitly modified to use a table lookup for performance reasons.

I'd be fine with not generating PyUnicode_IsWhiteSpace at all, but instead hand-coding it. I suspect that we might want to use more of PropList at some point, so an effort to parse it might not be wasted.