fields_security_contracts/views/templates.xml

<?xml version="1.0" encoding="UTF-8"?>
<openerp>
    <data>
        <template id="security_fields_contracts_assets" inherit_id="eiru_assets.assets">
            <xpath expr="." position="inside">
                <link rel="stylesheet" href="/fields_security_contracts/static/src/css/custom.css" />
            </xpath>
        </template>
    </data>
</openerp>