reverted:
--- b/core/modules/system/lib/Drupal/system/Plugin/Validation/Constraint/NotNullConstraint.php
+++ /dev/null
@@ -1,32 +0,0 @@
-<?php
-
-/**
- * @file
- * Definition of Drupal\Core\Validation\Constraint\NotNullConstraint.
- */
-
-use Drupal\Core\Annotation\Plugin;
-use Drupal\Core\Annotation\Translation;
-
-namespace Drupal\system\Plugin\Validation\Constraint;
-
-/**
- * Check if a value is not NULL.
- *
- * @Plugin(
- *   id = "notnull",
- *   label = @Translation("NotNull")
- * )
- */
-class NotNullConstraint implements \Drupal\Core\Validation\Constraint\ConstraintInterface {
-
-  /**
-   * Validate a constraint.
-   *
-   * @return boolean
-   *   TRUE if the value is not NULL, FALSE if the value is NULL.
-   */
-  public function validate($value) {
-     return !is_null($value); 
-  }
-}
only in patch2:
unchanged:
--- /dev/null
+++ b/core/lib/Drupal/Core/Plugin/Validation/Constraint/NotNullConstraint.php
@@ -0,0 +1,32 @@
+<?php
+
+/**
+ * @file
+ * Definition of Drupal\Core\Plugin\Validation\Constraint\NotNullConstraint.
+ */
+
+use Drupal\Core\Annotation\Plugin;
+use Drupal\Core\Annotation\Translation;
+
+namespace Drupal\Core\Plugin\Validation\Constraint;
+
+/**
+ * Check if a value is not NULL.
+ *
+ * @Plugin(
+ *   id = "notnull",
+ *   label = @Translation("NotNull")
+ * )
+ */
+class NotNullConstraint implements \Drupal\Core\Validation\Constraint\ConstraintInterface {
+
+  /**
+   * Validate a constraint.
+   *
+   * @return boolean
+   *   TRUE if the value is not NULL, FALSE if the value is NULL.
+   */
+  public function validate($value) {
+     return !is_null($value); 
+  }
+}