http://stackoverflow.com/questions/39520667/nskeyedunarchiver-not-working-with-swift-3

Open.swift

func open(_ filePath: String) throws -> NSArray {
    let data = try Data(contentsOf: URL(fileURLWithPath: filePath))
    let object: Any?
    if #available(OSX 10.11, *) {
        object = try NSKeyedUnarchiver.unarchiveTopLevelObjectWithData(data as NSData)
    } else {
        let unarchiver = NSKeyedUnarchiver(forReadingWith: data)
        object = unarchiver.decodeObject(forKey: "root")
    }
    guard let unarchivedObject = object else {
        throw ArchiveError.unableToUnarchive
    }
    guard let array = unarchivedObject as? NSArray else {
        throw ArchiveError.notArray
    }
    return array
}

enum ArchiveError: Error {
    case unableToUnarchive
    case notArray
}

In further refinement, I'd (a) not have try in the name of the method; and (b) retire use of NSException (we're throwing errors, not exceptions).