Comment 3 for bug 2059796

I had killed the authentication agent and forgot to bring it back, so my last comment conclusion is wrong.

The incorrect behavior does seem to be tied to deb822; for .source files the exception being suppressed is

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Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/softwareproperties/gtk/SoftwarePropertiesGtk.py", line 1158, in on_remove_clicked
    self.backend.RemoveSource(str(source_entry))
  File "/usr/lib/python3/dist-packages/dbus/proxies.py", line 141, in __call__
    return self._connection.call_blocking(self._named_service,
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3/dist-packages/dbus/connection.py", line 634, in call_blocking
    reply_message = self.send_message_with_reply_and_block(
                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
dbus.exceptions.DBusException: org.freedesktop.DBus.Python.ValueError: Traceback (most recent call last):
  File "/lib/python3/dist-packages/dbus/service.py", line 712, in _message_cb
    retval = candidate_method(self, *args, **keywords)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/lib/python3/dist-packages/softwareproperties/dbus/SoftwarePropertiesDBus.py", line 285, in RemoveSource
    self.remove_source(_to_unicode(source))
  File "/lib/python3/dist-packages/softwareproperties/SoftwareProperties.py", line 779, in remove_source
    self.remove_source(source, True)
  File "/lib/python3/dist-packages/softwareproperties/SoftwareProperties.py", line 781, in remove_source
    self.remove_source(source, False)
  File "/lib/python3/dist-packages/softwareproperties/SoftwareProperties.py", line 802, in remove_source
    self.sourceslist.list.append(SourceEntry("", file=source.file))
                                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/lib/python3/dist-packages/aptsources/sourceslist.py", line 509, in __init__
    raise ValueError("Classic SourceEntry cannot be written to .sources file")
ValueError: Classic SourceEntry cannot be written to .sources file
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