This was the only failure on 2 of 4 buildbots when I last looked.

test_os has several methods like this:

    def test_dup2(self):
        if hasattr(os, "dup2"):
            self.check(os.dup2, 20)

Should the hasattr be moved to skipUnless for all of these?
They now 'pass' without the needed os method.