use Symfony\Component\Form\Extension\Core\DataMapper\PropertyPathMapper;
 use Symfony\Component\Form\FormConfigBuilderInterface;
+use Symfony\Component\Form\Extension\Core\DataMapper\DataMapper;
+use Symfony\Component\Form\Extension\Core\DataAccessor\PropertyPathAccessor;

 class SomeClass
 {
     public function run(FormConfigBuilderInterface $builder)
     {
-        $builder->setDataMapper(new PropertyPathMapper());
+        $builder->setDataMapper(new DataMapper(new PropertyPathAccessor()));
     }
 }

 use Symfony\Component\Form\Extension\Core\DataMapper\PropertyPathMapper;

 class SomeClass
 {
     public function run()
     {
-        return new PropertyPathMapper();
+        return new \Symfony\Component\Form\Extension\Core\DataMapper\DataMapper(new \Symfony\Component\Form\Extension\Core\DataAccessor\PropertyPathAccessor());
     }
 }