old_contents: # -*- coding: utf-8 -*-
  from openerp import api, models
  
  
  class account_voucher(models.Model):
      _inherit = 'account.voucher'
  
      @api.multi
      def button_register_and_print(self):
          self.ensure_one()
          # register/confirm
          self.button_proforma_voucher()
          self.receipt_print()
  
new_contents: # -*- coding: utf-8 -*-
  from openerp import api, models
  
  
  class account_voucher(models.Model):
      _inherit = 'account.voucher'
  
      @api.multi
      def button_register_and_print(self):
          self.ensure_one()
          # register/confirm
          self.button_proforma_voucher()
          return self.receipt_print()
  
subject: FIX popup