Merge branch '2.8' into 3.4

* 2.8:
  Fix CS
  Allow reuse of Session between requests
  Provide debug_backtrace with proper args
  forward false label option to nested types
  forward the invalid_message option in date types

Author: nicolas-grekas

Tests/Dumper/PhpDumperTest.php

@@ -390,8 +390,8 @@ public function testResolvedBase64EnvParameters()
         $container->compile(true);
 
         $expected = array(
-          'env(foo)' => 'd29ybGQ=',
-          'hello' => 'world',
+            'env(foo)' => 'd29ybGQ=',
+            'hello' => 'world',
         );
         $this->assertSame($expected, $container->getParameterBag()->all());
     }