Odoo 12.  I'm trying to add chatter to the product.supplierinfo table as I have added a menu and view to see all of the alternate products in one view. In the product app, models - product.py, i've modified the following:

class SupplierInfo(models.Model):
     _name = "product.supplierinfo"
     _description = "Supplier Pricelist"

     _inherit = ['mail.thread', 'mail.activity.mixin']    

     _order = 'sequence, min_qty desc, price'

but after restarting the service, I get the following error:

psycopg2.ProgrammingError: column product_supplierinfo.message_main_attachment_id does not exist

Any help would be greatly appreciated.

thanks,

Dave