minor #24385 [FrameworkBundle] Register a NullLogger from test kernels (ogizanagi)

This PR was merged into the 3.4 branch.

Discussion
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[FrameworkBundle] Register a NullLogger from test kernels

| Q             | A
| ------------- | ---
| Branch?       | 3.4 <!-- see comment below -->
| Bug fix?      | no
| New feature?  | no <!-- don't forget updating src/**/CHANGELOG.md files -->
| BC breaks?    | no
| Deprecations? | no <!-- don't forget updating UPGRADE-*.md files -->
| Tests pass?   | yes
| Fixed tickets | N/A <!-- #-prefixed issue number(s), if any -->
| License       | MIT
| Doc PR        | N/A

Relates to #24300

This will avoid unnecessary output on Travis or when running FrameworkBundle tests locally:
- before: https://travis-ci.org/symfony/symfony/jobs/281624658#L3594-L3635
- after: https://travis-ci.org/symfony/symfony/jobs/281643868#L3599-L3617

but also needed for anyone running functional tests on their project and using the default logger, in order to not get garbage output.

Do we need to find a more generic solution (like exposing a `framework.default_logger` option so users can set it to false for test)? Or just documenting this?

Commits
-------

c109dcd5ae [FrameworkBundle] Register a NullLogger from test kernels

src/Symfony/Bundle/FrameworkBundle/Tests/Command/CacheClearCommand/Fixture/TestAppKernel.php

@@ -11,8 +11,10 @@
 
 namespace Symfony\Bundle\FrameworkBundle\Tests\Command\CacheClearCommand\Fixture;
 
+use Psr\Log\NullLogger;
 use Symfony\Bundle\FrameworkBundle\FrameworkBundle;
 use Symfony\Component\Config\Loader\LoaderInterface;
+use Symfony\Component\DependencyInjection\ContainerBuilder;
 use Symfony\Component\HttpKernel\Kernel;
 
 class TestAppKernel extends Kernel
@@ -33,4 +35,9 @@ class TestAppKernel extends Kernel
     {
         $loader->load(__DIR__.DIRECTORY_SEPARATOR.'config.yml');
     }
+
+    protected function build(ContainerBuilder $container)
+    {
+        $container->register('logger', NullLogger::class);
+    }
 }

src/Symfony/Bundle/FrameworkBundle/Tests/Functional/app/AppKernel.php

@@ -11,7 +11,9 @@
 
 namespace Symfony\Bundle\FrameworkBundle\Tests\Functional\app;
 
+use Psr\Log\NullLogger;
 use Symfony\Component\Config\Loader\LoaderInterface;
+use Symfony\Component\DependencyInjection\ContainerBuilder;
 use Symfony\Component\Filesystem\Filesystem;
 use Symfony\Component\HttpKernel\Kernel;
 
@@ -72,6 +74,11 @@ class AppKernel extends Kernel
         $loader->load($this->rootConfig);
     }
 
+    protected function build(ContainerBuilder $container)
+    {
+        $container->register('logger', NullLogger::class);
+    }
+
     public function serialize()
     {
         return serialize(array($this->varDir, $this->testCase, $this->rootConfig, $this->getEnvironment(), $this->isDebug()));

src/Symfony/Bundle/FrameworkBundle/Tests/Kernel/ConcreteMicroKernel.php

@@ -11,6 +11,7 @@
 
 namespace Symfony\Bundle\FrameworkBundle\Tests\Kernel;
 
+use Psr\Log\NullLogger;
 use Symfony\Bundle\FrameworkBundle\Kernel\MicroKernelTrait;
 use Symfony\Bundle\FrameworkBundle\FrameworkBundle;
 use Symfony\Component\Config\Loader\LoaderInterface;
@@ -77,6 +78,7 @@ class ConcreteMicroKernel extends Kernel implements EventSubscriberInterface
 
     protected function configureContainer(ContainerBuilder $c, LoaderInterface $loader)
     {
+        $c->register('logger', NullLogger::class);
         $c->loadFromExtension('framework', array(
             'secret' => '$ecret',
         ));