UIDocument Creation on iOS 11: reader is not permitted to access the URL

This is a repost from StackOverflow.

Since iOS 11 I have encountered the following error every time I am creating a new document using `UIDocument` API:

[ERROR] Could not get attribute values for item /var/mobile/Containers/Data/Application/
XXXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXX/Documents/myDoc-XXXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXX.myFile (n).
Error: Error Domain=NSFileProviderInternalErrorDomain Code=1 "The reader is not permitted to access the URL."
UserInfo={NSLocalizedDescription=The reader is not permitted to access the URL.}

Unlike similar questions asked online, I am not using `UIDocumentBrowserViewController`. I am simply creating a UIDocument and call `save()` to the `Documents` directory myself. The closest question I found uses `UIManagedDocument`. However, in my case, the file is still created and written successfully despite the error message.

Here's the gist of my save routine:

    @IBAction func createDoc(_ sender: Any) {
        let uuid = UUID().uuidString
        let doc = Document(baseName: "myDoc-\(uuid)")
        doc.save(to: doc.fileURL, for: .forCreating) { (completed) in
            if (completed) {
                doc.close(completionHandler: nil)
                self.verifyNumberOfFiles()
            }
        }
    }

My Document subclass is also almost blank for simplicity of this question:

    class Document: UIDocument {   
       
        let fileExtension = "myFile"
       
        override init(fileURL url: URL) {
            super.init(fileURL: url)
        }
        /
        convenience init(baseName: String) {
            self.init(fileURL: documentsDirectory.appendingPathComponent(baseName).appendingPathExtension(Document.fileExtension))
        }
       
        override func contents(forType typeName: String) throws -> Any {
            return NSData()
        }
       
        override func load(fromContents contents: Any, ofType typeName: String?) throws {
           
        }
       
    }

I'm always writing to `Documents` folder, and my lookup routine can verify that my files are successfully created:

    public var documentsDirectory: URL {
        return FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).last!
    }
    func loadFileURLs(from dirURL: URL) -> [URL]? {
        return try? FileManager().contentsOfDirectory(at: dirURL, includingPropertiesForKeys: nil)
    }

What I have discovered so far:

- The error appears even when I set up my UTI already. I can verify that my UTI works when I send a "myFile" to my device over AirDrop and it correctly triggers my app to open.

- The error appears on iOS 11 only. The same code doesn't reproduce the error on iOS 10.

- I tried adding `UISupportsDocumentBrowser` key although I'm not using the browser but it's not dissolve the error.

What is happening? Is this just a "noise" error message on iOS 11?

Here's my GitHub code online if anyone is interested.