Xcode 8 can't open Model.xcdatamodeld
<p>I am running macOS Sierra (Build 16A320), using Xcode 8.0 (8A218a) and have migrated all my code to Swift 3.</p>

<p>I can't open my <code>Model.xcdatamodeld</code> file anymore. Selecting it in the project navigator does not open up the "Core Data Model editor" view (not sure what it is called). I have tried restarting Xcode, but it does not work. I have tried deleting derived data, cleaning, does not work. I have tried double clicking, does not work.</p>

<p><code>Model.xcdatamodeld</code> is visible in the Project navigator view, but it is not <strong>possible to interact with it</strong> (other than right clicking), <strong>nothing happens when I click or double click on it</strong>.</p>

<p><strong>EDIT: Problem solved, see <a href="https://stackoverflow.com/a/39626959/1311272">my answer below</a></strong></p>