social/mass_mailing_custom_unsubscribe/views/pages.xml

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

<template name="Unsubscription worked"
          id="website.mass_mail_unsubscription_success"
          page="True">
    <t t-call="website.layout">
        <div id="wrap" class="oe_structure oe_empty">
            <section class="jumbotron mt16 mb16">
                <div class="container">
                    <h1>
                        You were successfully unsubscribed from our
                        mailing list
                    </h1>
                    <h3 class="text-muted">
                        It's sad to see you go, but if you love
                        something, let it go.
                    </h3>
                    <p>
                        However, we are open to suggestions. Please tell us
                        why you left.
                    </p>
                    <p>
                        <a class="btn btn-primary btn-lg"
                           href="/page/website.contactus">Contact us</a>
                    </p>
                </div>
            </section>
        </div>
    </t>
</template>

<template name="Unsubscription failed"
          id="website.mass_mail_unsubscription_failure"
          page="True">
    <t t-call="website.layout">
        <div id="wrap" class="oe_structure oe_empty">
            <section class="jumbotron mt16 mb16">
                <div class="container">
                    <h1>
                        There was an error processing your unsubscription
                        request
                    </h1>
                    <p>
                        We apologize for the inconvinience. You can contact us
                        and we will handle your unsubscription manually.
                    </p>
                    <p>Thanks for your patience.</p>
                    <p>
                        <a class="btn btn-primary btn-lg"
                           href="/page/website.contactus">Contact us</a>
                    </p>
                </div>
            </section>
        </div>
    </t>
</template>

</data>
</openerp>