title: PyQt5 - "Cannot set X11 selection owner" error when using .setMimeData() on Ubuntu 16.04
body: <p>Keep Getting this error when using PyQt5's <code>clipboard.setMimeData()</code></p>
  
  <p><code>QXcbClipboard::setMimeData: Cannot set X11 selection owner</code></p>
  
  <pre><code>def copy(index, app):
      clipboard = app.clipboard()
      Mode = clipboard.Clipboard
  
      initialMimeData = clipboard.mimeData(mode = Mode)
  
      import pyautogui
      pyautogui.hotkey('ctrl', 'c')
  
      mimeData = clipboard.mimeData(mode = Mode)
      clipboards[index-1]["Data"] = mimeData
      clipboard.setMimeData(initialMimeData, mode = Mode) #getting the error here
  </code></pre>
  
  <p>I'm running this on Ubuntu 16.04. Why do I get this issue and how do I fix it?</p>