message: add missing enum
diff: @@ -14,7 +14,7 @@ use {coin,fee};
  use coin::{Coin, CoinDiff};
  use fee::{FeeAlgorithm, Fee};
  use std::iter::Iterator;
  -use std::{result, iter, fmt, error, cmp::{min,max}};
  +use std::{result, iter, fmt, error};
  /// Transaction Builder composed of inputs, outputs
  #[derive(Clone)]
  @@ -40,6 +40,7 @@ impl fmt::Display for Error {
  match self {
  Error::TxInvalidNoInput => write!(f, "Transaction is invalid, no input."),
  Error::TxInvalidNoOutput => write!(f, "Transaction is invalid, no output."),
  + Error::TxNotEnoughTotalInput => write!(f, "Transaction is invalid, already not enough input coins."),
  Error::TxOverLimit(sz) => write!(f, "Transaction too big, current size is {} bytes but limit size is {}.", sz, TX_SIZE_LIMIT),
  Error::TxSignaturesExceeded => write!(f, "Transaction has already enough signatures"),
  Error::TxSignaturesMismatch => write!(f, "Number of signatures does not match the number of witnesses"),
  