when I try to create a new subgroup. The name of the new group is check for global uniqueness. If this group name already exists in a different group I got an error: //IntegrityError: (IntegrityError) column group_name is not unique u'INSERT INTO groups (group_name, group_parent_id, group_description) VALUES (?, ?, ?)' ...//
It should be sufficient to have unique names only in the subgroup where the new group is going to be added.