@Override
  public long getChainHeadBlockNumber() {
    throw new NonDeterministicOperationException(CHAIN_HEAD_ERROR);
  }
Create a new blockchain object for T8n testing.

@param referenceTestEnv the referenfe test environment, containing most of the block header
    stuff
@param protocolSpec the protocol spec, which impacts what block header fields are implemente.
ethereum/evmtool/src/main/java/org/hyperledger/besu/evmtool/t8n/T8nBlockchain.java