When my Opportunity goes from the stage new to qualified, I need odoo to create a project containing certain tasks following a given template. 

For that I tried to create a product "Project creation", which is a service and whose sale should create a project following my template. Therefore, the stage change on my opportunity should create a sale order, on which a quotation template is defined and for which the customer is the same as the opportunity's customer. 

This is where I have a problem, if i try to set sale_order.partner_id = record.partner_id.  I get this error : 

psycopg2.ProgrammingError: can't adapt type 'res.partner' 

If I do not set this line, I also get an error as a sale cannot be created without a customer. 

Where does this error come from ? Is there another way to do this ?