Merge branch '3.4' into 4.3

* 3.4:
  Various tweaks 3.4
  [PhpUnit] Fix usleep mock return value
  [Lock] use Predis\ClientInterface instead of Predis\Client

Author: nicolas-grekas

Loader/PhpFileLoader.php

@@ -40,7 +40,7 @@ public function load($file, $type = null)
 
         // the closure forbids access to the private scope in the included file
         $loader = $this;
-        $load = \Closure::bind(static function ($file) use ($loader) {
+        $load = \Closure::bind(static function ($file) {
             return include $file;
         }, null, ProtectedPhpFileLoader::class);