Merge branch '3.4' into 4.2

* 3.4:
  [Phpunit] fixed support for PHP 5.3
  Response prepare method update
  [Workflow] Added missing license header
  Check if Client exists when test.client does not exist, to provide clearer exception message
  [Form] Preventing validation of children if parent with Valid constraint has no validation groups
  [Tests] fixed compatbility of assertEquals(): void
  [Intl] Fix test
  [Validator] Add the missing translations for the Arabic (ar) locale
  [Intl] Add compile binary
  [Form] Fixed some phpdocs

Author: fabpot

Test/WebTestCase.php

@@ -36,7 +36,10 @@ protected static function createClient(array $options = [], array $server = [])
         try {
             $client = $kernel->getContainer()->get('test.client');
         } catch (ServiceNotFoundException $e) {
-            throw new \LogicException('You cannot create the client used in functional tests if the BrowserKit component is not available. Try running "composer require symfony/browser-kit".');
+            if (class_exists(Client::class)) {
+                throw new \LogicException('You cannot create the client used in functional tests if the "framework.test" config is not set to true.');
+            }
+            throw new \LogicException('You cannot create the client used in functional tests if the BrowserKit component is not available. Try running "composer require symfony/browser-kit"');
         }
 
         $client->setServerParameters($server);