I can't answer that for the 'LOGNAME' environment variable on non-Windows systems, I was just keying off of what the docs claimed. As for Windows, I just came across this article http://support.microsoft.com/kb/273633 that shows we can not rely on this in the test.  

I only put those environment variables in the test because I thought this test was a little weak (what else can we do?)

    user_name = os.getlogin()
    self.assertNotEqual(0, len(user_name))

Even though %USERNAME% == os.getlogin() MOST of the time. It should be removed from the test.