LocalizedMessage

If the Accept-Language header in the incoming request is not "English", then errors returned by the Apps Script API include this message. It contains the same error text translated to the requested locale.

JSON representation 
{
  "locale": string,
  "message": string
}
Fields
locale

string

The locale used following the specification defined at https://www.rfc-editor.org/rfc/bcp/bcp47.txt. Examples are: "en-US", "fr-CH", "es-MX"
message

string

The localized error message in the above locale.