I disagree. They're a warning and an error message, and should go to stderr.
It may _also_ be useful to show them on the terminal, in case the user would like to see them now, and has redirected stderr somewhere other than the terminal. In that case a program might show them on /dev/tty as well.
It may _also_ be useful to show them on the terminal, in case the user would like to see them now, and has redirected stderr somewhere other than the terminal. In that case a program might show them on /dev/tty as well.