event_sale_report.xml

<?xml version="1.0" encoding="utf-8"?>
<openerp>
    <data>

    <record id="paperformat_euro_lowmargin" model="report.paperformat">
        <field name="name">European A4 low margin</field>
        <field name="default" eval="True" />
        <field name="format">A4</field>
        <field name="page_height">0</field>
        <field name="page_width">0</field>
        <field name="orientation">Portrait</field>
        <field name="margin_top">5</field>
        <field name="margin_bottom">5</field>
        <field name="margin_left">5</field>
        <field name="margin_right">5</field>
        <field name="header_line" eval="False" />
        <field name="header_spacing">0</field>
        <field name="dpi">80</field>
    </record>
    <report 
        id="action_report_registrationbadge"
        model="event.registration" 
        string="Badge"
        report_type="qweb-html"
        name="event_sale.report_registrationbadge"
        file="event_sale.report_registrationbadge"
    />
    <record id="action_report_registrationbadge" model="ir.actions.report.xml">
        <field name="paperformat_id" ref="event_sale.paperformat_euro_lowmargin"/>
    </record>

    </data>
</openerp>