Comment 6 for bug 1262150

Just to help people wanting to remove the module base_partner_merge, or any other module overloading a base field such as 'id' or 'create_date', the trick is to remove the xmlid corresponding to the field, before removing the module.
Go to settings → Technical → Sequences & identifiers → external identifiers → search 'merge' in Module → delete the two xmlids. Then uninstall the module.