@Override
  public Optional<String> getInvalidReason() {
    return (validationResult.isValid()
        ? Optional.empty()
        : Optional.of(validationResult.getErrorMessage()));
  }
Returns the reason why a transaction was reverted (if applicable).

@return the revert reason.
ethereum/core/src/main/java/org/hyperledger/besu/ethereum/processing/TransactionProcessingResult.java