-v writes to stderr, so this is the expected behavior. Although maybe this could be better documented.

See issue 18338, where this was briefly discussed and a change was rejected.

Maybe you're looking for -V (uppercase) or --version, which do write to stdout, at least in 3.x. I'm not sure where they write in 2.7, but it's much too late to change 2.7's behavior.

I'm going to close this. If you find some of our documentation that says -v writes to stdout, then we can reopen this.

This is not a Windows specific error, so I'm modifying the nosy list.