web/web_environment_ribbon/view/base_view.xml

<?xml version="1.0" encoding="utf-8"?>
<!-- Copyright 2015 Francesco OpenCode Apruzzese <cescoap@gmail.com>
     Copyright 2016 Antonio Espinosa <antonio.espinosa@tecnativa.com>
     License AGPL-3.0 or later (http://www.gnu.org/licenses/agpl). -->
<odoo>

<!-- Load css for ribbons -->
<template id="assets_backend" name="ribbon_test assets"
          inherit_id="web.assets_backend">
    <xpath expr="." position="inside">
        <link rel="stylesheet"
              href="/web_environment_ribbon/static/src/css/ribbon.css"/>
        <script type="text/javascript"
                src="/web_environment_ribbon/static/src/js/ribbon.js"/>
    </xpath>
</template>

</odoo>