Using event('response-status-code')

gistfile1.xml

<xhtml:html xmlns:ev="http://www.w3.org/2001/xml-events" xmlns:fr="http://orbeon.org/oxf/xml/form-runner" xmlns:xforms="http://www.w3.org/2002/xforms" xmlns:xhtml="http://www.w3.org/1999/xhtml" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:xxforms="http://orbeon.org/oxf/xml/xforms">
    <xhtml:head>
        <xforms:model>
            <xforms:submission id="inexistent" resource="http://www.orbeon.com/gaga" replace="instance" method="post">
                <xforms:message ev:event="xforms-submit-error" level="modal">submission1 error (<xforms:output value="event('response-status-code')"/>)</xforms:message>
            </xforms:submission>
            <xforms:instance>
                <instance/>
            </xforms:instance>
        </xforms:model>
    </xhtml:head>
    <xhtml:body>
    <xforms:trigger appearance="minimal">
        <xforms:label>Submit</xforms:label>
        <xforms:send ev:event="DOMActivate" submission="inexistent"/>
    </xforms:trigger>
    </xhtml:body>
</xhtml:html>