'Override to update the issue according to the email.'

@api.multi
def message_update(self, msg, update_vals=None):

    email_list = self.email_split(msg)
    partner_ids = filter(None, self._find_partner_from_emails(email_list))
    self.message_subscribe(partner_ids)
    return super(ProjectIssue, self).message_update(msg, update_vals=update_vals)
