如何在Xcode 8 beta中使SpriteKit Playgrounds工作？

我希望能够在Playgrounds中轻松制作我的Sprite Kit代码原型。在Xcode 7中工作正常

import UIKit
import SpriteKit
import XCPlayground


let sceneView = SKView(frame: CGRect(x:0 , y:0, width: 480, height: 320))

let scene = SKScene(size: CGSize(width: 480, height: 320))
sceneView.showsFPS = true
sceneView.presentScene(scene)
XCPlaygroundPage.currentPage.liveView = sceneView

let square = SKSpriteNode(imageNamed: "square")
square.name = "shape"
square.position = CGPoint(x: scene.size.width * 0.25, y: scene.size.height * 0.5)

let circle = SKSpriteNode(imageNamed: "circle")
circle.name = "shape"
circle.position = CGPoint(x: scene.size.width * 0.50, y: scene.size.height * 0.5)

let triangle = SKSpriteNode(imageNamed: "triangle")
triangle.name = "shape"
triangle.position = CGPoint(x: scene.size.width * 0.75, y: scene.size.height * 0.5)

scene.addChild(square)
scene.addChild(circle)
scene.addChild(triangle)

在Xcode 7中，我得到了一个不错的实时视图

这只是在Swift 3和8.0 beta 3（8S174q）中不起作用。我必须改变什么？