Comment 1 for bug 1199984

Here is the Traceback for the error:

Traceback (most recent call last):
  File "/usr/lib/ubuntu-release-upgrader/check-new-release-gtk", line 137, in on_button_upgrade_now_clicked
    res = fetcher.run()
  File "/usr/lib/python3/dist-packages/DistUpgrade/DistUpgradeFetcherCore.py", line 278, in run
    _("Fetching the upgrade failed. There may be a network "
  File "/usr/lib/python3/dist-packages/DistUpgrade/DistUpgradeFetcher.py", line 50, in error
    return error(self.window_main, summary, message)
  File "/usr/lib/python3/dist-packages/DistUpgrade/utils.py", line 442, in error
    buttons=Gtk.ButtonsType.CLOSE)
  File "/usr/lib/python3/dist-packages/gi/overrides/Gtk.py", line 503, in __init__
    **kwds)
  File "/usr/lib/python3/dist-packages/gi/overrides/Gtk.py", line 434, in __init__
    self.set_transient_for(parent)
  File "/usr/lib/python3/dist-packages/gi/types.py", line 47, in function
    return info.invoke(*args, **kwargs)
TypeError: argument parent: Expected Gtk.Window, but got __main__.CheckNewReleaseGtk