Code snippet to block author pages

So you can remove the author-pages with an author.php file in your (child) theme, but what if you don’t want to touch the theme you ask? Well, I just added this code snippet to two of the sites I manage to stop user-enumeration (which can be done on any WordPress site by going to /index.php?author=1):

add_action('wp','no_author_page');
function no_author_page() {
  if (is_author()) {
    global $wp_query;
    $wp_query->set_404();
    status_header( 404 );
    get_template_part( 404 );
    exit();
  }
}

Disclaimer: the bulk of above code was shamelessly copy/ pasted from https://wordpress.stackexchange.com/a/27124