Skip the intl notice if run with phpunit

src/Symfony/Bundle/FrameworkBundle/DependencyInjection/FrameworkExtension.php

@@ -205,7 +205,7 @@ class FrameworkExtension extends Extension
                     ->addError('You cannot use the "slugger" service since the Translation contracts are not installed. Try running "composer require symfony/translation".');
             }
 
-            if (!\extension_loaded('intl')) {
+            if (!\extension_loaded('intl') && !\defined('PHPUNIT_COMPOSER_INSTALL')) {
                 @trigger_error('Please install the "intl" PHP extension for best performance.', E_USER_DEPRECATED);
             }
         }

src/Symfony/Bundle/FrameworkBundle/Tests/Functional/SluggerLocaleAwareTest.php

@@ -16,6 +16,9 @@ namespace Symfony\Bundle\FrameworkBundle\Tests\Functional;
  */
 class SluggerLocaleAwareTest extends AbstractWebTestCase
 {
+    /**
+     * @requires extension intl
+     */
     public function testLocalizedSlugger()
     {
         $kernel = static::createKernel(['test_case' => 'Slugger', 'root_config' => 'config.yml']);