Issue with the JSON example for Stormy

import UIKit

class ViewController: UIViewController {

    private let apiKey = "redacted"

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
        let baseURL = NSURL(
            string: "https://api.forecast.io/forecast/\(apiKey)/"
        )
        let forecastURL = NSURL(
            string: "37.8267,-122.423",
            relativeToURL: baseURL
        )

        let sharedSession = NSURLSession.sharedSession()
        let downloadTask: NSURLSessionDownloadTask =
        sharedSession.downloadTaskWithURL(
            forecastURL!,
            completionHandler:
            {
                (
                    location: NSURL!,
                    response:NSURLResponse!,
                    error:NSError!
                ) -> Void in
                var urlContents = NSString(
                    contentsOfURL: location,
                    encoding: NSUTF8StringEncoding,
                    error: nil
                )
                println(urlContents)
            }
        )
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }


}