title: kCFPreferencesAnyUser with a container is only allowed for System Containers
body: <p>I have an app that shares preferences with a Today extension, following the approach described in many places (like <a href="http://blog.intrepid.io/ios-app-extensions" rel="noreferrer">this</a>), i.e., creating and registering an App Group, then loading preferences:</p>
  
  <pre><code>if let ud = UserDefaults(suitName: "group.myshop.MyDefaultsSuite") {
    let myPref = ud.string(forKey: "myUserName")
    ...
  }
  </code></pre>
  
  <p>This worked fine through about April, 2016, and I didn't touch the app for a long time. Then I downloaded the latest Xcode (v8.3.3) and updated my code for Swift 3 as reflected above.</p>
  
  <p>However, now on the <code>ud.string()</code> line I get a console warning <code>Using kCFPreferencesAnyUser with a container is only allowed for System Containers, detaching from cfprefsd</code>. And my preferences fail to load. I've seen <a href="https://stackoverflow.com/questions/38275395/failed-to-read-values-in-cfprefsplistsource-ios-10#">other issues posted</a> that look very similar, but no solutions. I'd rather not rename my preferences bundle or pre-pend my group ID as that would effectively block access to previously saved settings.</p>
  
  <p>Has anyone else found a solution?</p>