Fix for this error:

Fatal error: Access level to Sonata\MediaBundle\Listener\ODM\MediaEventSubscriber::recomputeSingleEntityChangeSet() must be protected (as in class Sonata\MediaBundle\Listener\BaseMediaEventSubscriber) or weaker in ..../vendor/sonata-project/media-bundle/Sonata/MediaBundle/Listener/ODM/MediaEventSubscriber.php on line 19

Listener/ODM/MediaEventSubscriber.php

@@ -36,7 +36,7 @@ public function getSubscribedEvents()
      * @param \Doctrine\Common\EventArgs $args
      * @return void
      */
-    private function recomputeSingleEntityChangeSet(EventArgs $args)
+    protected function recomputeSingleEntityChangeSet(EventArgs $args)
     {
         $em = $args->getDocumentManager();