swift2 – Playground Xcode：无法获得沙箱扩展

2015-10-28 16:28:45.159 Playground[83944:17501939] Failed to obtain sandbox extension for path=/var/folders/h7/cbc1x51x2rs7sjzfk0ndtxkr0000gp/T/com.apple.dt.Xcode.pg/containers/

我所做的是：

>开始了Xcode 7 / Swift 2项目
>使用“pod install Alamofire”
>使用以下代码创建.playground文件：

进口Alamofire

Alamofire.request(.GET,"http://httpbin.org/get",parameters: ["foo": "bar"]).responseJSON { response in

        print(response.request)  // original URL request
        print(response.response) // URL response
        print(response.data)     // server data
        print(response.result)   // result of response serialization

        let str = response.data!

        if let JSON = response.result.value {
            print("JSON: (JSON)")
        }
}

如何在.playground文件中测试此库而不会出错？