server-tools/base_user_role/data/ir_cron.xml

<?xml version="1.0" encoding="utf-8" ?>
<!-- Copyright 2016 ABF OSIELL <http://osiell.com>
     License LGPL-3.0 or later (http://www.gnu.org/licenses/lgpl).
 -->
<odoo noupdate="1">
    <record model="ir.cron" id="cron_update_users">
        <field name='name'>Update user roles</field>
        <field name='interval_number'>3</field>
        <field name='interval_type'>hours</field>
        <field name="numbercall">-1</field>
        <field name="active">True</field>
        <field name="doall" eval="False" />
        <field name="model_id" ref="base_user_role.model_res_users_role" />
        <field name="state">code</field>
        <field name="code">model.cron_update_users()</field>
    </record>
</odoo>