docs: def btc_make_data_script( data, **ignored ):
      """
      Make a data-bearing transaction output.
      Data must be a hex string
      Returns a hex string.
      """
      if len(data) >= MAX_DATA_LEN * 2:
          raise ValueError("Data hex string is too long")     # note: data is a hex string
  
      if len(data) % 2 != 0:
          raise ValueError("Data hex string is not even length")
  
      return "6a{:02x}{}".format(len(data)/2, data)