Require authors to set featured image for post

Question

I have customised my Wordpress site design to use the featured image for posts quite excessively. This is why I need to require all post made by non-admins to require a set

Answer 1

Given Gary's example above, I've written the following to my functions.php file:

function featured_image_requirement() {
     if(!has_post_thumbnail()) {
          wp_die( 'You forgot to set the featured image. Click the back button on your browser and set it.' ); 
     } 
}
add_action( 'pre_post_update', 'featured_image_requirement' );

I'd much rather see this in a plugin as well - there's one called Mandatory Field but it doesn't work with scheduled posts. Both are not really eloquent solutions.