ImportError: cannot import name 'CalendarWeek' from 'aleksis.apps.chronos.util' (unknown location)

File "/home/dolphi/Projects/AlekSIS/AlekSIS/apps/official/AlekSIS-App-Alsijil/aleksis/apps/alsijil/urls.py", line 3, in <module>
    from . import views
  File "/home/dolphi/Projects/AlekSIS/AlekSIS/apps/official/AlekSIS-App-Alsijil/aleksis/apps/alsijil/views.py", line 15, in <module>
    from aleksis.apps.chronos.util import CalendarWeek
ImportError: cannot import name 'CalendarWeek' from 'aleksis.apps.chronos.util' (unknown location)