use the forward compat version in the Filesystem service

src/Symfony/Bundle/FrameworkBundle/Resources/config/services.xml

@@ -7,7 +7,7 @@
     <parameters>
         <parameter key="event_dispatcher.class">Symfony\Bundle\FrameworkBundle\ContainerAwareEventDispatcher</parameter>
         <parameter key="http_kernel.class">Symfony\Bundle\FrameworkBundle\HttpKernel</parameter>
-        <parameter key="filesystem.class">Symfony\Component\HttpKernel\Util\Filesystem</parameter>
+        <parameter key="filesystem.class">Symfony\Component\Filesystem\Filesystem</parameter>
         <parameter key="cache_warmer.class">Symfony\Component\HttpKernel\CacheWarmer\CacheWarmerAggregate</parameter>
         <parameter key="file_locator.class">Symfony\Component\HttpKernel\Config\FileLocator</parameter>
     </parameters>