Seems like something similar to odoo/odoo#17111 can happen on Python 2.
The same change as #17111 is a bit involved for -stable, but this looks
pretty harmless.
Probably fixes#23781.
The group base.group_user is used in the computation of the share column which
is executed at column creation, before the group is imported.
Set it in base.sql to already have an xmlid to resolve.