anchor.diff:     * unknown analysis option was provided.
      */
     Response.unknownAnalysisOption(Request request, String optionName)
  -    : this(request.id, 'Unknown analysis option: "$optionName"');
  +    : this(request.id, new RequestError(-6, 'Unknown analysis option: "$optionName"'));
   
     /**
      * Initialize a newly created instance to represent an error condition caused
      * by a [request] that cannot be handled by any known handlers.
      */
     Response.unknownRequest(Request request)
  -    : this(request.id, 'Unknown request');
  +    : this(request.id, new RequestError(-7, 'Unknown request'));
   
     /**
      * Return the value of the result field with the given [name].
  
positive.code:    * passed a non-boolean value.
     */
    Response.expectedBoolean(Request request, String value)
      : this(request.id, 'Expected a boolean value, but found "$value"');
  
    /**
     * Initialize a newly created instance to represent an error condition caused
  
negative.code:   /**
     * Convert the given [value] to a boolean, or throw a [RequestFailure]
     * exception if the [value] could not be converted.
     *
     * The value is typically the result of invoking either [getParameter] or
     * [getRequiredParameter].
     */
  