It goes to /dev/null, which is (mostly) what we want. We're already capturing all errors on the JS side with the Logger class, so there shouldn't be any data going to this. On the off chance that an extension decides to write to stderr instead of console, we don't want the error messages polluting our communication channel on stdout.

I could imagine doing something complicated like parsing this separately and dumping it to NSLog. But really, this is not the way people should be debugging stuff on the node side, so I don't think we should encourage it.

I've added a comment explaining this in the code.