Merge branch '3.4' into 4.0

* 3.4: (22 commits)
  [DI] Add tests for EnvVarProcessor
  [Bridge\PhpUnit] Fix #26430 Cannot autoload listeners
  Make sure we always render errors. Eventhough labels are disabled
  Make sure form errors is valid HTML
  [HttpKernel] Allow generators in registerBundle
  [TwigBundle] document TwigRenderer BC break in UPGRADE-3.4
  Extra line to bootstrap 3 horizontal layout
  [Serializer] Remove const override
  Update Client.php
  [PhpUnitBridge] Ability to use different composer.json file
  [DomCrawler] FormField: remove an useless return statement
  [Config] ReflectionClassResource check abstract ServiceSubscriberInterface and EventSubscriberInterface
  Display the Welcome Page when there is no homepage defined
  fix regression when extending the Container class without a constructor
  fix the updating of timestamp in the MemcachedSessionHandler
  [SecurityBundle] Make extra character non mandatory in regex
  [Config] Add characters to the regex
  bumped Symfony version to 3.4.7
  updated VERSION for 3.4.6
  updated CHANGELOG for 3.4.6
  ...

Author: nicolas-grekas

Field/FormField.php

@@ -75,8 +75,6 @@ public function getLabel()
         if ($labels->length > 0) {
             return $labels->item(0);
         }
-
-        return;
     }
 
     /**