code: function errorify (res) {
    var cwd = process.cwd()
    var count = res.errorCount + res.warningCount
    var err = new Error('' + count + (count === 1 ? ' issue' : ' issues') + ' found:')
    err.stack = '' + err.message
  
    res.results.forEach(function (result) {
      result.messages.forEach(function (message) {
        err.stack += ('\n    ' +
          result.filePath.replace(cwd, '').replace(/^\//, '') +
          ':' + message.line + ':' + message.column + ': ' +
          message.message + ' (' + message.ruleId + ')')
      })
    })
  
    return err
  }
docs: /*
  returns an Error object from a standard `results` object.