Issue #2550641 by damiankloip: Use assert() in Drupal\Core\DependencyInjection\Container::__sleep instead of trigger error

core/lib/Drupal/Core/DependencyInjection/Container.php

@@ -31,7 +31,7 @@ class Container extends DrupalContainer {
    * {@inheritdoc}
    */
   public function __sleep() {
-    trigger_error('The container was serialized.', E_USER_ERROR);
+    assert(FALSE, 'The container was serialized.');
     return array_keys(get_object_vars($this));
   }
 

core/lib/Drupal/Core/DependencyInjection/ContainerBuilder.php

@@ -118,7 +118,7 @@ class ContainerBuilder extends SymfonyContainerBuilder {
    * {@inheritdoc}
    */
   public function __sleep() {
-    trigger_error('The container was serialized.', E_USER_ERROR);
+    assert(FALSE, 'The container was serialized.');
     return array_keys(get_object_vars($this));
   }
 

core/tests/Drupal/Tests/Core/DependencyInjection/ContainerBuilderTest.php

@@ -70,4 +70,14 @@ class ContainerBuilderTest extends UnitTestCase {
     $container->register('Bar');
   }
 
+  /**
+   * Tests serialization.
+   *
+   * @expectedException \AssertionError
+   */
+  public function testSerialize() {
+    $container = new ContainerBuilder();
+    serialize($container);
+  }
+
 }

core/tests/Drupal/Tests/Core/DependencyInjection/ContainerTest.php

@@ -20,7 +20,7 @@ class ContainerTest extends UnitTestCase {
   /**
    * Tests serialization.
    *
-   * @expectedException \PHPUnit_Framework_Error
+   * @expectedException \AssertionError
    */
   public function testSerialize() {
     $container = new Container();