code: private AmazonServiceException createException(String errorCode, JsonContent jsonContent) {
          AmazonServiceException ase = unmarshallException(errorCode, jsonContent);
          if (ase == null) {
              ase = new AmazonServiceException(
                      "Unable to unmarshall exception response with the unmarshallers provided");
          }
          return ase;
      }
docs: Create an AmazonServiceException using the chain of unmarshallers. This method will never
  return null, it will always return a valid AmazonServiceException
  
  @param errorCode
  Error code to find an appropriate unmarshaller
  @param jsonContent
  JsonContent of HTTP response
  @return AmazonServiceException