private static string FormatError(LiquidError x)
        {
            // to remain backwards-compatible, this leaves "Liquid Error:" alone.
            String err = x.Message;

            if (!String.IsNullOrWhiteSpace(x.TokenSource))
            {
                err = x.ToString();
            }
            if (x.Message.IndexOf("Liquid error") >= 0)
            {
                return(err);
            }
            else
            {
                return("ERROR: " + err);
            }
        }