Fix constrain validation, increase error message and remove depreceated @api.one.
Fix constrain validation, increase error message and remove depreceated @api.one.

rvalyi/l10n-brazil,odoo-brazil/l10n-brazil-wip,odoo-brazil/l10n-brazil-wip,thinkopensolutions/l10n-brazil,thinkopensolutions/l10n-brazil,rvalyi/l10n-brazil