Change status message text

Let's say that a contrib module is showing a message like this: Your message has been created, and you want to change it to something like this: Message created. To do this you don't have to hack the contrib module, you can use the hook_preprocess_HOOK() to alter the message.

/**
 * Implements hook_preprocess_HOOK().
 */
function MY_MODULE_preprocess_status_messages(&$variables) {
  if (isset($variables['message_list']['status'])){
    $status_messages = $variables['message_list']['status'];
    foreach($status_messages as $delta => $message) {
      if (strpos((string) $message, 'Your message has been created.') !== FALSE) {
        $variables['message_list']['status'][$delta] = t('Message created.');
      }
    }
  }
}