old_contents: from mechanic.registry import Registry
  from mechanic.ui.windows.main import MechanicWindow
  from mechanic.ui.windows.notification import UpdateNotificationWindow
  
  window = MechanicWindow('install')
  tab = window.current_tab.view
  table = tab.content.list
  
  table.set(Registry('http://www.robofontmechanic.com').all())
  tab.enable()
  
  def dummy_updates(self, *args, **kwargs): return ['updates']
  
  UpdateNotificationWindow.get_updates = dummy_updates
  UpdateNotificationWindow()
  
new_contents: from mechanic.registry import Registry
  from mechanic.ui.windows.main import MechanicWindow
  from mechanic.ui.windows.notification import UpdateNotificationWindow
  
  window = MechanicWindow().open('install')
  tab = window.current_tab.view
  table = tab.list
  
  table.set(Registry('http://www.robofontmechanic.com').extensions())
  tab.enable()
  
  def dummy_updates(self, *args, **kwargs): return ['updates']
  
  UpdateNotificationWindow.get_updates = dummy_updates
  UpdateNotificationWindow()
  
subject: fix demo script