Trytond-admin could not delete user

Not so good… worked on the dev db. On the production copy, raises

30362 140481034299136 [2019-02-07 00:47:26,529] ERROR trytond.convert Could not delete id: 10 of model res.user
There should be some relation that points to this resource
You should manually fix this and restart --update=module
Traceback (most recent call last):
  File "/home/tryton/venv/lib/python3.5/site-packages/trytond/convert.py", line 797, in post_import
    Model.delete([Model(db_id)])
  File "/home/tryton/venv/lib/python3.5/site-packages/trytond/res/user.py", line 414, in delete
    cls.raise_user_error('delete_forbidden')
  File "/home/tryton/venv/lib/python3.5/site-packages/trytond/error.py", line 74, in raise_user_error
    raise UserError(error)
trytond.exceptions.UserError: ('UserError', ('Les utilisateurs ne peuvent pas être supprimé pour des raisons de journalisation.\nVous devez les désactiver à la place.', ''))
30362 140481034299136 [2019-02-07 00:47:26,555] ERROR trytond.convert Could not delete id: 9 of model res.user
There should be some relation that points to this resource
You should manually fix this and restart --update=module
Traceback (most recent call last):
  File "/home/tryton/venv/lib/python3.5/site-packages/trytond/convert.py", line 797, in post_import
    Model.delete([Model(db_id)])
  File "/home/tryton/venv/lib/python3.5/site-packages/trytond/res/user.py", line 414, in delete
    cls.raise_user_error('delete_forbidden')
  File "/home/tryton/venv/lib/python3.5/site-packages/trytond/error.py", line 74, in raise_user_error
    raise UserError(error)
trytond.exceptions.UserError: ('UserError', ('Les utilisateurs ne peuvent pas être supprimé pour des raisons de journalisation.\nVous devez les désactiver à la place.', ''))

User 9 and 10 are Cron Process Sale and Purchase. Why does trytond-admin want to delete them? and fail?

They are tryied to delete because the are no longer defined on the new modules (this error is from ugrade to 5.0). You can ignore this errors: See Issue 7771: Users can not be deleted for logging purpose - Tryton issue tracker for more details