old_contents: # -*- coding: utf-8 -*-
  # © 2016 ClearCorp
  # License AGPL-3.0 or later (http://www.gnu.org/licenses/agpl.html).
  
  from openerp import models, fields, api
  from datetime import date
  from openerp.exceptions import Warning
  
  
  class ResPartner(models.Model):
  
      _inherit = 'res.partner'
  
      slow_payer = fields.Boolean('Slow payer', compute='_compute_slow_payer')
  
      @api.multi
      def _compute_slow_payer(self):
          today = date.today().strftime('%d-%m-%Y')
          for partner in self:
              invoice = self.env['account.invoice'].search(
                  [('partner_id', '=', partner.id),
                   ('date_due', '<', today),
                   ('state', '=', 'open')])
              if invoice:
                  partner.slow_payer = True
                  return True
              else:
                  return False
  
  
  class AccountInvoice(models.Model):
  
      _inherit = 'account.invoice'
  
      @api.multi
      def invoice_validate(self):
          if not self.env.user.has_group(
                  'partner_slow_payer.group_partner_slow_payer'):
              if self.partner_id.slow_payer:
                  raise Warning('You have a pending invoice')
              elif self.partner_id.credit_limit == 0.0:
                  raise Warning('You credit is in cero')
              else:
                  super(AccountInvoice, self).invoice_validate()
          else:
              super(AccountInvoice, self).invoice_validate()
  
  
  class SaleOrder(models.Model):
  
      _inherit = 'sale.order'
  
      @api.multi
      def action_wait(self):
          super(SaleOrder, self).action_wait()
          if not self.env.user.has_group(
                  'partner_slow_payer.group_partner_slow_payer'):
              if self.partner_id.credit_limit == 0.0:
                  raise Warning('You credit is in cero')
              elif self.partner_id.slow_payer:
                  raise Warning('You have a pending invoice')
  
new_contents: # -*- coding: utf-8 -*-
  # © 2016 ClearCorp
  # License AGPL-3.0 or later (http://www.gnu.org/licenses/agpl.html).
  
  from openerp import models, fields, api
  from datetime import date
  from openerp.exceptions import Warning
  
  
  class ResPartner(models.Model):
  
      _inherit = 'res.partner'
  
      slow_payer = fields.Boolean('Slow payer', compute='_compute_slow_payer')
  
      @api.multi
      def _compute_slow_payer(self):
          today = date.today().strftime('%d-%m-%Y')
          for partner in self:
              invoice = self.env['account.invoice'].search(
                  [('partner_id', '=', partner.id),
                   ('date_due', '<', today),
                   ('state', '=', 'open')])
              if invoice:
                  partner.slow_payer = True
              else:
                  partner.slow_payer = False
  
  
  class AccountInvoice(models.Model):
  
      _inherit = 'account.invoice'
  
      @api.multi
      def invoice_validate(self):
          for invoice in self:
              if not self.env.user.has_group(
                      'partner_slow_payer.group_partner_slow_payer'):
                  if invoice.partner_id.slow_payer:
                      raise Warning('You have a pending invoice')
                  if invoice.partner_id.credit_limit - invoice.partner_id.credit - \
                          invoice.amount_total <= 0.0:
                      raise Warning('You credit is in cero')
          super(AccountInvoice, self).invoice_validate()
  
  
  class SaleOrder(models.Model):
  
      _inherit = 'sale.order'
  
      @api.multi
      def action_wait(self):
          super(SaleOrder, self).action_wait()
          for sale in self:
              if not self.env.user.has_group(
                      'partner_slow_payer.group_partner_slow_payer'):
                  if sale.partner_id.credit_limit - sale.partner_id.credit - \
                          sale.amount_total <= 0.0:
                      raise Warning('You credit is in cero')
                  if sale.partner_id.slow_payer:
                      raise Warning('You have a pending invoice')
  
subject: change the validation of credit limit exeption