Merge branch '4.3' into 4.4

* 4.3:
  [ProxyManager] fix generating proxies for root-namespaced classes
  [DI] skip looking for config class when the extension class is anonymous
  Fix typo
  [Dotenv] FIX missing getenv
  [HttpClient][Psr18Client] Remove Psr18ExceptionTrait

Author: nicolas-grekas

Extension/Extension.php

@@ -80,6 +80,11 @@ public function getAlias()
     public function getConfiguration(array $config, ContainerBuilder $container)
     {
         $class = \get_class($this);
+
+        if (false !== strpos($class, "\0")) {
+            return null; // ignore anonymous classes
+        }
+
         $class = substr_replace($class, '\Configuration', strrpos($class, '\\'));
         $class = $container->getReflectionClass($class);