Traceback (most recent call last):
  File "/usr/bin/update-manager", line 112, in <module>
    from DistUpgrade.DistUpgradeController import DistUpgradeController
  File "/usr/lib/python3/dist-packages/DistUpgrade/DistUpgradeController.py", line 65, in <module>
    from .DistUpgradeQuirks import DistUpgradeQuirks
  File "/usr/lib/python3/dist-packages/DistUpgrade/DistUpgradeQuirks.py", line 40, in <module>
    from janitor.plugincore.manager import PluginManager
ImportError: No module named plugincore.manager