Merge branch '4.3' into 4.4

* 4.3:
  cs fix
  Fix inconsistent return points.
  [Config] Add handling for ignored keys in ArrayNode::mergeValues.
  Fix inconsistent return points.
  [Security/Core] UserInterface::getPassword() can return null
  [Router] Fix TraceableUrlMatcher behaviour with trailing slash
  Revert "bug #33092 [DependencyInjection] Improve an exception message (fabpot)"

Author: nicolas-grekas

ServiceSubscriberTrait.php

@@ -57,5 +57,7 @@ public function setContainer(ContainerInterface $container)
         if (\is_callable(['parent', __FUNCTION__])) {
             return parent::setContainer($container);
         }
+
+        return null;
     }
 }