任何遇到此线程的人，@ LeoDabus都向我指出了在哪里关闭沙箱的方法，

Anyone coming across this thread, @LeoDabus pointed me to where to turn off sandbox, which worked:

他还整理了一下我的代码:

He also cleaned up my code a bit:

let fileURL = URL( fileURLWithPath: "/Users/me/file.txt" )    
var rawDataString: String
var errorString: String?

do {
    rawDataString = try String( contentsOf: fileURL, encoding: .utf8 )
} catch let error as NSError {
    errorString = error.description
    rawDataString = ""
    return
}