ubuntu-release-upgrader crashed with AttributeError: '_NamespacePath' object has no attribute 'sort'

The traceback happens when importing computer janitor code which no longer need.

Traceback (most recent call last):
  File "/tmp/ubuntu-release-upgrader-lj_9ymon/bionic", line 8, in <module>
    sys.exit(main())
  File "/tmp/ubuntu-release-upgrader-lj_9ymon/DistUpgrade/DistUpgradeMain.py", line 224, in main
    from .DistUpgradeController import DistUpgradeController
  File "/tmp/ubuntu-release-upgrader-lj_9ymon/DistUpgrade/DistUpgradeController.py", line 52, in <module>
    from .DistUpgradeQuirks import DistUpgradeQuirks
  File "/tmp/ubuntu-release-upgrader-lj_9ymon/DistUpgrade/DistUpgradeQuirks.py", line 36, in <module>
    from janitor.plugincore.manager import PluginManager
  File "/tmp/ubuntu-release-upgrader-lj_9ymon/janitor/__init__.py", line 20, in <module>
    import pkg_resources
  File "/usr/lib/python3/dist-packages/pkg_resources/__init__.py", line 2927, in <module>
    @_call_aside
  File "/usr/lib/python3/dist-packages/pkg_resources/__init__.py", line 2913, in _call_aside
    f(*args, **kwargs)
  File "/usr/lib/python3/dist-packages/pkg_resources/__init__.py", line 2952, in _initialize_master_working_set
    add_activation_listener(lambda dist: dist.activate())
  File "/usr/lib/python3/dist-packages/pkg_resources/__init__.py", line 956, in subscribe
    callback(dist)
  File "/usr/lib/python3/dist-packages/pkg_resources/__init__.py", line 2952, in <lambda>
    add_activation_listener(lambda dist: dist.activate())
  File "/usr/lib/python3/dist-packages/pkg_resources/__init__.py", line 2515, in activate
    declare_namespace(pkg)
  File "/usr/lib/python3/dist-packages/pkg_resources/__init__.py", line 2097, in declare_namespace
    _handle_ns(packageName, path_item)
  File "/usr/lib/python3/dist-packages/pkg_resources/__init__.py", line 2047, in _handle_ns
    _rebuild_mod_path(path, packageName, module)
  File "/usr/lib/python3/dist-packages/pkg_resources/__init__.py", line 2066, in _rebuild_mod_path
    orig_path.sort(key=position_in_sys_path)
AttributeError: '_NamespacePath' object has no attribute 'sort'

This bug was fixed in the package ubuntu-release-upgrader - 1:19.04.5

---------------
ubuntu-release-upgrader (1:19.04.5) disco; urgency=medium

  * Remove the unused computer janitor code thereby resolving a Traceback that
    occurs when importing it. (LP: #1805475)

 -- Brian Murray <email address hidden> Tue, 27 Nov 2018 09:17:35 -0800