Python: Problems with Windows

I guess I should have just copied over curl in the first place. Turns out that Python's implementation of tempfile.mkstemp() makes a temporary file so secure that nothing can get into it after you close() it, not even the exact same script. I'm not entirely sure why I'm seeing this:

    os.rename(tmpfn,fn)
OSError: [Errno 13] Permission denied

But I am. This has so not been worth it, as the whole point was having a .py file that I could run (with identical behavior, natch) on OS X, BSD, and Windows. No such luck! curl.exe, here I come.