code: function req (params, spec, errs) {
    for (var key in spec) {
      if (spec[key].req && !params.hasOwnProperty(key)) reqError(key, errs)
    }
  }
docs: Ensure that required keys are set.
  
  @param {Object} params
  Parameters value object.
  
  @param {String} spec
  Parameters definition object.
  
  @param {Array} errs
  Errors list.