extra argument 'error' in callのエラーが解決できません

extra argument 'error' in callというエラーが解決できません。
以下のコードの、

swift
1        let results: NSArray! = memoContext.executeFetchRequest(memoRequest, error: nil)

の部分でエラーが出ています。
Xcode7.1でswift2を使用しています。
どのように書き換えたら解決できますでしょうか。

swift
1import UIKit
2import CoreData
3
4class ViewController: UIViewController {
5    
6    var memoField: UITextField!
7    
8    var memos: [NSString] = []
9    var dates: [NSDate] = []
10    
11    
12    override func viewDidLoad() {
13        super.viewDidLoad()
14        
15        // text field
16        memoField = UITextField(frame: CGRectMake(100, 100, 200, 30))
17        memoField.borderStyle = UITextBorderStyle.RoundedRect
18        self.view.addSubview(memoField)
19        
20        // write button
21        let writeBtn: UIButton = UIButton(frame: CGRectMake(100, 150, 200, 30))
22        writeBtn.backgroundColor = UIColor.magentaColor()
23        writeBtn.setTitle("write", forState: UIControlState.Normal)
24        writeBtn.addTarget(self, action: "writeData", forControlEvents: UIControlEvents.TouchUpInside)
25        self.view.addSubview(writeBtn)
26        
27        // read button
28        let readBtn: UIButton = UIButton(frame: CGRectMake(100, 200, 200, 30))
29        readBtn.backgroundColor = UIColor.orangeColor()
30        readBtn.setTitle("read", forState: UIControlState.Normal)
31        readBtn.addTarget(self, action: "readData", forControlEvents: UIControlEvents.TouchUpInside)
32        self.view.addSubview(readBtn)
33        
34    }
35    
36    override func didReceiveMemoryWarning() {
37        super.didReceiveMemoryWarning()
38    }
39    
40    func writeData() {
41        let appDel: AppDelegate = UIApplication.sharedApplication().delegate as! AppDelegate
42        let memoContext: NSManagedObjectContext = appDel.managedObjectContext
43        let memoEntity: NSEntityDescription! = NSEntityDescription.entityForName("TodoData", inManagedObjectContext: memoContext)
44        let newData = TodoData(entity: memoEntity, insertIntoManagedObjectContext: memoContext)
45        newData.todo = memoField.text!
46        newData.time = NSDate()
47    }
48    
49    func readData() {
50        let appDel: AppDelegate = UIApplication.sharedApplication().delegate as! AppDelegate
51        let memoContext: NSManagedObjectContext = appDel.managedObjectContext
52        let memoRequest: NSFetchRequest = NSFetchRequest(entityName: "TodoData")
53        memoRequest.returnsObjectsAsFaults = false
54        let results: NSArray! = memoContext.executeFetchRequest(memoRequest, error: nil)
55        
56            
57        memos = []
58        dates = []
59        
60        for data in results {
61            memos.append(data.todo)
62            dates.append(data.time)
63        }
64
65    }
66}