As per our client’s requirement we had to add few functionality in existing openerp sale module so we implemented it by our custom module without touching the existing module.
Usualy this is a very basic thing but sometimes in this process we get an error, In odoo we have sale. order in sale module, and if we create another custom module which uses sale.order and if we don’t include sale in the dependency of our custom module then we get this error.
TypeError: The model “sale.order” specifies an unexisting parent class “sale.order”
Above Error occurs either because you have not added module dependency in “__openerp__.py” or you have used “_inherit” instead of “_name”.
‘You may need to add a dependency on the parent class\’ module.’ % (name, parent_name))
You have to write module dependency in the __openerp__.py which contain _name=’sale.order’.
By doing this you will be able to proceed further.