[IMP] point_of_sale: log error message too
[IMP] point_of_sale: log error message too

It's needed in phantomjs tests.

Without this commit it printed only error stack, which doesn't provide enough
information to fix it. This is a problem when the error is not reproduced on
running tours manually in browser.

ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo