Merge branch '3.4' into 4.2

* 3.4:
  cs fix
  cs fix
  [PHPUnit-Bridge] override some environment variables
  [TwigBridge] Remove use spaceless tag
  [translation] Update defaut format from yml to yaml
  Change default log level for output streams
  update docblock to match the actual behavior
  compatibility with phpunit8
  [Debug][DebugClassLoader] Detect annotations before blank docblock lines on final and internal methods
  Added translations for chineese language.

Author: nicolas-grekas

Tests/Command/TranslationUpdateCommandTest.php

@@ -159,7 +159,7 @@ private function createCommandTester($extractedMessages = [], $loadedMessages =
             ->expects($this->any())
             ->method('getFormats')
             ->will(
-                $this->returnValue(['xlf', 'yml'])
+                $this->returnValue(['xlf', 'yml', 'yaml'])
             );
 
         if (null === $kernel) {