Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/softwareproperties/gtk/DialogCacheOutdated.py", line 86, in on_pktask_finish
    results = self._pktask.generic_finish(result)
gi.repository.GLib.GError: pk-client-error-quark: W: GPG error: http://ddebs.ubuntu.com eoan-updates Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY C8CAB6595FDFF622
E: The repository 'http://ddebs.ubuntu.com eoan-updates Release' is not signed.
W: Updating from such a repository can't be done securely, and is therefore disabled by default.
W: See apt-secure(8) manpage for repository creation and user configuration details.
W: GPG error: http://ddebs.ubuntu.com eoan-proposed Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY C8CAB6595FDFF622
E: The repository 'http://ddebs.ubuntu.com eoan-proposed Release' is not signed.
 (319)

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/softwareproperties/gtk/DialogCacheOutdated.py", line 89, in on_pktask_finish
    Gtk.ButtonsType.CANCEL, _("Error while refreshing cache"))
  File "/usr/lib/python3/dist-packages/gi/overrides/__init__.py", line 319, in new_init
    return super_init_func(self, **new_kwargs)
  File "/usr/lib/python3/dist-packages/gi/overrides/Gtk.py", line 575, in __init__
    self._init(*args, **new_kwargs)
  File "/usr/lib/python3/dist-packages/gi/overrides/__init__.py", line 319, in new_init
    return super_init_func(self, **new_kwargs)
  File "/usr/lib/python3/dist-packages/gi/overrides/Gtk.py", line 521, in __init__
    _window_init(self, *args, **kwargs)
  File "/usr/lib/python3/dist-packages/gi/overrides/__init__.py", line 319, in new_init
    return super_init_func(self, **new_kwargs)
TypeError: could not convert value for property `transient_for' from DialogCacheOutdated to GtkWindow