Updating the uom_id on a product_product will eventually change also the
uom_po_id to have them belonging to the same category. Saving the update
call write() on product with a dict of two values (uom_id and uom_po_id)
As product.product is inherited from product.template, the write() on
the corresponding product_template is called but in this case 2 times
for each values. The first time, only uom_id is updated. The _check_uom
constraint is triggered and obviously failed. The uom_po_id on the
template is not yet updated.
This commit makes the sync in the beginning of write() of product.template.
Which means before calling the constraint.
This commit also makes the onchanges on uom_id acts the same between
product.product and product.template.
Task : 2197818
closesodoo/odoo#48714
Signed-off-by: Arnold Moyaux <amoyaux@users.noreply.github.com>