ENGCOM-3940: [Backport] Added required error message. #20509

 - Merge Pull Request #20509 from mageprince/magento2:2.2-develop-PR-port-19870
 - Merged commits:
   1. ce11dd1
   2. a10e313
   3. b14ad81
   4. 6235266
   5. fc67582
   6. aea6e3b
   7. c0d6a65

Author: magento-engcom-team

lib/internal/Magento/Framework/Serialize/Serializer/Json.php

@@ -16,27 +16,27 @@
 class Json implements SerializerInterface
 {
     /**
-     * {@inheritDoc}
+     * @inheritDoc
      * @since 100.2.0
      */
     public function serialize($data)
     {
         $result = json_encode($data);
         if (false === $result) {
-            throw new \InvalidArgumentException('Unable to serialize value.');
+            throw new \InvalidArgumentException("Unable to serialize value. Error: " . json_last_error_msg());
         }
         return $result;
     }
 
     /**
-     * {@inheritDoc}
+     * @inheritDoc
      * @since 100.2.0
      */
     public function unserialize($string)
     {
         $result = json_decode($string, true);
         if (json_last_error() !== JSON_ERROR_NONE) {
-            throw new \InvalidArgumentException('Unable to unserialize value.');
+            throw new \InvalidArgumentException("Unable to unserialize value. Error: " . json_last_error_msg());
         }
         return $result;
     }