'Adds a foreman rule for this hunt.'

def _AddForemanRule(self):

    foreman_rule = rdf_foreman.ForemanRule(created=rdfvalue.RDFDatetime.Now(), expires=self.context.expires, description=('Hunt    %s    %s' % (self.session_id, self.runner_args.hunt_name)), client_rule_set=self.runner_args.client_rule_set)
    foreman_rule.actions.Append(hunt_id=self.session_id, hunt_name=self.runner_args.hunt_name, client_limit=self.runner_args.client_limit)
    foreman_rule.Validate()
    with aff4.FACTORY.Open('aff4:/foreman', mode='rw', token=self.token, aff4_type=aff4_grr.GRRForeman) as foreman:
        foreman_rules = foreman.Get(foreman.Schema.RULES, default=foreman.Schema.RULES())
        foreman_rules.Append(foreman_rule)
        foreman.Set(foreman_rules)
