Merge branch '4.3' into 4.4

* 4.3:
  [Serializer] add missing "internal" annotation
  [DI] Fix suspicious test
  [SecurityBundle] add missing contraint for symfony/config dep

Tests/Compiler/ValidateEnvPlaceholdersPassTest.php

@@ -278,16 +278,15 @@ public function testEnvWithVariableNode(): void
 
     /**
      * @group legacy
+     * @expectedDeprecation A tree builder without a root node is deprecated since Symfony 4.2 and will not be supported anymore in 5.0.
      */
     public function testConfigurationWithoutRootNode(): void
     {
         $container = new ContainerBuilder();
         $container->registerExtension(new EnvExtension(new EnvConfigurationWithoutRootNode()));
-        $container->loadFromExtension('env_extension');
+        $container->loadFromExtension('env_extension', ['foo' => 'bar']);
 
-        $this->doProcess($container);
-
-        $this->addToAssertionCount(1);
+        (new ValidateEnvPlaceholdersPass())->process($container);
     }
 
     public function testEmptyConfigFromMoreThanOneSource()
@@ -392,7 +391,7 @@ class EnvConfigurationWithoutRootNode implements ConfigurationInterface
 {
     public function getConfigTreeBuilder()
     {
-        return new TreeBuilder('env_extension');
+        return new TreeBuilder();
     }
 }