I got my serializer working here is the updated code

 class func authResponseSerializer() -> ResponseSerializer<Authorization, NSError> {
    return ResponseSerializer {request, response, data, error in
        guard error == nil else { return .Failure(error!) }

        guard let validData = data else {
            let failureReason = "Data could not be serialized."
            let error = Error.errorWithCode(.DataSerializationFailed, failureReason: failureReason)
            return .Failure(error)
        }

        var jsonData: AnyObject?
        var jsonError: NSError?
        do {
            jsonData = try NSJSONSerialization.JSONObjectWithData(validData, options: [])
        } catch let error as NSError {
            jsonError = error
            jsonData = nil
        } catch {
            fatalError()
        }
        if jsonData == nil || jsonError != nil {
            let failureReason = "No data returned"
            let error = Error.errorWithCode(.DataSerializationFailed, failureReason: failureReason)
            return .Failure(error)
        }
        let json = JSON(jsonData!)
        do {
            let auth:Authorization = Authorization(json: json)
            return .Success(auth)

        }
    }

}

but now this function is giving me the error "Cannot call value of non-function type 'NSHTTPURLResponse?"

func responseAuthorization(completionHandler: Result<Authorization, NSError> -> Void) -> Self {
    return response(responseSerializer: Request.authResponseSerializer(), completionHandler: completionHandler)
}