bug #24563 [Serializer] ObjectNormalizer: throw if PropertyAccess isn't installed (dunglas)

This PR was squashed before being merged into the 2.7 branch (closes #24563).

Discussion
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[Serializer] ObjectNormalizer: throw if PropertyAccess isn't installed

| Q             | A
| ------------- | ---
| Branch?       | 2.7
| Bug fix?      | yes
| New feature?  | no <!-- don't forget to update src/**/CHANGELOG.md files -->
| BC breaks?    | no
| Deprecations? | no <!-- don't forget to update UPGRADE-*.md files -->
| Tests pass?   | yes
| Fixed tickets | #24553
| License       | MIT
| Doc PR        | n/a

Commits
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b5246a72ca [Serializer] ObjectNormalizer: throw if PropertyAccess isn't installed

src/Symfony/Component/Serializer/Normalizer/ObjectNormalizer.php

@@ -16,6 +16,7 @@ use Symfony\Component\PropertyAccess\PropertyAccess;
 use Symfony\Component\PropertyAccess\PropertyAccessorInterface;
 use Symfony\Component\Serializer\Exception\CircularReferenceException;
 use Symfony\Component\Serializer\Exception\LogicException;
+use Symfony\Component\Serializer\Exception\RuntimeException;
 use Symfony\Component\Serializer\Mapping\Factory\ClassMetadataFactoryInterface;
 use Symfony\Component\Serializer\NameConverter\NameConverterInterface;
 
@@ -33,6 +34,10 @@ class ObjectNormalizer extends AbstractNormalizer
 
     public function __construct(ClassMetadataFactoryInterface $classMetadataFactory = null, NameConverterInterface $nameConverter = null, PropertyAccessorInterface $propertyAccessor = null)
     {
+        if (!class_exists('Symfony\Component\PropertyAccess\PropertyAccess')) {
+            throw new RuntimeException('The ObjectNormalizer class requires the "PropertyAccess" component. Install "symfony/property-access" to use it.');
+        }
+
         parent::__construct($classMetadataFactory, $nameConverter);
 
         $this->propertyAccessor = $propertyAccessor ?: PropertyAccess::createPropertyAccessor();