public static ResultType merge(ResultType t1, ResultType t2) {
      if (t1 == ResultType.ERROR || t2 == ResultType.ERROR) {
        return ResultType.ERROR;
      }
      if (t1 == ResultType.CONTINUE || t2 == ResultType.CONTINUE) {
        return ResultType.CONTINUE;
      }
      return ResultType.END;
    }
Indicates an unrecoverable error was raised.
portability-spi-transfer/src/main/java/org/datatransferproject/spi/transfer/provider/ExportResult.java