social/mail_digest/views/user_views.xml

<?xml version="1.0"?>
<openerp>
    <data>

        <record id="notifications_email_user_info_form" model="ir.ui.view">
            <field name="name">mail.notifications res.users.form</field>
            <field name="model">res.users</field>
            <field name="inherit_id" ref="mail.view_users_form_mail"/>
            <field name="arch" type="xml">
                <xpath expr="//field[@name='notify_email']" position="after">
                    <field name="notify_frequency" attrs="{'invisible': [('notify_email','=', 'none')]}" />
                    <field name="notify_conf_ids" attrs="{'invisible': [('notify_email','=', 'none')]}" />
                </xpath>
            </field>
        </record>

    </data>
</openerp>