Make a "fake" txid for the genesis block history
    Returns a 32-byte hash (single sha256), hex-encoded
    (single sha256 so it can be easily verified against our genesis block tooling)

def namedb_genesis_block_history_hash(genesis_block_history):
    """
    Make a "fake" txid for the genesis block history
    Returns a 32-byte hash (single sha256), hex-encoded
    (single sha256 so it can be easily verified against our genesis block tooling)
    """
    # no-whitespace sorted serialization
    preimage = json.dumps(genesis_block_history, sort_keys=True, separators=(',',':'))
    h = hashlib.sha256(preimage).hexdigest()
    return h