Merge branch '2.8' into 3.1

* 2.8:
  Relax 1 test failing with latest PHP versions
  bumped Symfony version to 2.8.10
  Remove usage of __CLASS__ outside of a class
  [HttpKernel] Fix variable conflicting name
  [Process] Fix double-fread() when reading unix pipes
  [Process] Fix AbstractPipes::write() for a situation seen on HHVM (at least)
  [Validator] Fix dockblock typehint in XmlFileLoader
  bumped Symfony version to 2.8.10
  updated VERSION for 2.8.9
  updated CHANGELOG for 2.8.9
  bumped Symfony version to 2.7.17
  updated VERSION for 2.7.16
  update CONTRIBUTORS for 2.7.16
  updated CHANGELOG for 2.7.16
  Minor fixes
  [Console] Overcomplete argument exception message tweak.
  fixed bad auto merge
  Console table cleanup
  undefined offset fix (#19406)
  [EventDispatcher] Removed unused variable

Conflicts:
	CHANGELOG-2.7.md
	CHANGELOG-3.0.md
	src/Symfony/Bridge/Swiftmailer/DataCollector/MessageDataCollector.php
	src/Symfony/Bundle/FrameworkBundle/DependencyInjection/FrameworkExtension.php
	src/Symfony/Bundle/FrameworkBundle/Tests/DependencyInjection/FrameworkExtensionTest.php
	src/Symfony/Component/Console/Tests/Helper/LegacyDialogHelperTest.php
	src/Symfony/Component/Console/Tests/Helper/TableTest.php
	src/Symfony/Component/DependencyInjection/Tests/Fixtures/containers/legacy-container9.php
	src/Symfony/Component/EventDispatcher/Tests/AbstractEventDispatcherTest.php
	src/Symfony/Component/HttpFoundation/Tests/Session/Storage/Handler/LegacyPdoSessionHandlerTest.php
	src/Symfony/Component/HttpKernel/Kernel.php

Author: nicolas-grekas

Tests/DebugClassLoaderTest.php

@@ -13,7 +13,6 @@
 
 use Symfony\Component\Debug\DebugClassLoader;
 use Symfony\Component\Debug\ErrorHandler;
-use Symfony\Component\Debug\Exception\ContextErrorException;
 
 class DebugClassLoaderTest extends \PHPUnit_Framework_TestCase
 {