MAGETWO-51754: Fail automated test CreateProductAttributeEntityTest

Author: Bohdan Korablov

dev/tests/functional/tests/app/Magento/Catalog/Test/Constraint/AssertProductAttributeIsRequired.php

@@ -47,7 +47,8 @@ public function processAssert(
         $productForm->getAttributeElement($attribute)->setValue('');
         $catalogProductEdit->getFormPageActions()->save();
         $validationErrors = $productForm->getSection($sectionName)->getValidationErrors();
-        $actualMessage = $validationErrors[$attribute->getFrontendLabel()];
+        $actualMessage = isset($validationErrors[$attribute->getFrontendLabel()])
+            ? $validationErrors[$attribute->getFrontendLabel()] : '';
 
         \PHPUnit_Framework_Assert::assertEquals(
             self::REQUIRE_MESSAGE,