Update to drupal 8.0.0-rc1. For more information, see https://www.drupal.org/node/2582663

vendor/symfony/validator/Constraints/NotNullValidator.php

@@ -0,0 +1,38 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\Validator\Constraints;
+
+use Symfony\Component\Validator\Constraint;
+use Symfony\Component\Validator\ConstraintValidator;
+use Symfony\Component\Validator\Exception\UnexpectedTypeException;
+
+/**
+ * @author Bernhard Schussek <bschussek@gmail.com>
+ *
+ * @api
+ */
+class NotNullValidator extends ConstraintValidator
+{
+    /**
+     * {@inheritdoc}
+     */
+    public function validate($value, Constraint $constraint)
+    {
+        if (!$constraint instanceof NotNull) {
+            throw new UnexpectedTypeException($constraint, __NAMESPACE__.'\NotNull');
+        }
+
+        if (null === $value) {
+            $this->context->addViolation($constraint->message);
+        }
+    }
+}