title: Cannot add add-ons to v3.20.0 of orange
body: <p>I just upgraded my version of orange and the add-ons I used before are no longer there.  I went to add them but I get a python error.  Is there a fix?</p>
  
  <p><a href="https://i.stack.imgur.com/nNjBO.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/nNjBO.png" alt="enter image description here"></a></p>