title: Cron error old_api while running Schedule Action odoo 8
body: <p>I have created a function which is working fine if i use it through the view. but it's not working on schedule action, in openerp log show the following error.</p>
  
  <pre><code>TypeError: old_api() takes at least 4 arguments (3 given)
  </code></pre>
  
  <p>My module </p>
  
  <pre><code>class account_invoice(models.Model):
  _name = 'account.invoice'
  _rec_name = 'invoice_number'
  
  @api.multi
  def create_invoice(self):
      id = self.id
      amount = 0
      journal = self.env['journal.entry']
      for credit in self.invoice_line:
          fee = credit.amount * credit.qty
          if credit.account.parent.type.name == "Revenue":
              journal.sudo().create({'account': credit.account.id,
                                   'credit': fee,
                                   'student_id' : self.student_id.id})
  </code></pre>