code: function expandErrors(logger) {
      var oldLogFunc = logger.log
      logger.log = function() {
        var args = Array.prototype.slice.call(arguments, 0)
        if (args.length >= 2 && args[1] instanceof Error) {
          args[1] = args[1].stack
        }
        return oldLogFunc.apply(this, args)
      };
      return logger
    }
docs: Extend a winston by making it expand errors when passed in as the second argument (the first argument is the log level). <https://gist.github.com/johndgiese/59bd96360ce411042294> <https://gist.github.com/getvega/6211610>