Merge branch '2.8' into 3.1

* 2.8:
  Compatibility with Twig 1.27
  [VarDumper] Fix dumping Twig source in stack traces
  Enhance GAE compat by removing some realpath()
  bumped Symfony version to 2.8.14
  updated VERSION for 2.8.13
  updated CHANGELOG for 2.8.13
  bumped Symfony version to 2.7.21
  updated VERSION for 2.7.20
  update CONTRIBUTORS for 2.7.20
  updated CHANGELOG for 2.7.20
  [SecurityBundle] Fix twig-bridge lowest dep

Author: nicolas-grekas

DependencyInjection/AbstractDoctrineExtension.php

@@ -134,10 +134,7 @@ protected function setMappingDriverConfig(array $mappingConfig, $mappingName)
             throw new \InvalidArgumentException(sprintf('Invalid Doctrine mapping path given. Cannot load Doctrine mapping/bundle named "%s".', $mappingName));
         }
 
-        if (substr($mappingDirectory, 0, 7) !== 'phar://') {
-            $mappingDirectory = realpath($mappingDirectory);
-        }
-        $this->drivers[$mappingConfig['type']][$mappingConfig['prefix']] = $mappingDirectory;
+        $this->drivers[$mappingConfig['type']][$mappingConfig['prefix']] = realpath($mappingDirectory) ?: $mappingDirectory;
     }
 
     /**

DependencyInjection/CompilerPass/DoctrineValidationPass.php

@@ -61,7 +61,7 @@ private function updateValidatorMappingFiles(ContainerBuilder $container, $mappi
         foreach ($container->getParameter('kernel.bundles') as $bundle) {
             $reflection = new \ReflectionClass($bundle);
             if (is_file($file = dirname($reflection->getFileName()).'/'.$validationPath)) {
-                $files[] = realpath($file);
+                $files[] = $file;
                 $container->addResource(new FileResource($file));
             }
         }