Custom message on WP login page

Sometimes you just need to tell people something before they log in. Like, if your name is Pat Griffin, you're not allowed. (Pat Griffin is a friend of mine I worked with. We like to give each other a hard time. This is the kind of thing he would love.)

/*
    Add custom message to WordPress login page
*/
function SVS_login_message( $message ) {
    if ( empty($message) ){
        return "<p><strong>This login is only for Site Admins. If you are something else, please click the logo above and use the LOGIN link in the main menu.</strong></p>";
    } else {
        return $message;
    }
}
add_filter( 'login_message', 'SVS_login_message' );