odoo/addons/project_issue/res_config_view.xml

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

        <record id="view_config_settings" model="ir.ui.view">
            <field name="name">Project Application</field>
            <field name="model">project.config.settings</field>
            <field name="type">form</field>
            <field name="inherit_id" ref="project.view_config_settings"/>
            <field name="arch" type="xml">
                <div name="module_project_issue_sheet" position="after">
                    
                    <div>
                        <field name="fetchmail_issue" class="oe_inline"/>
                        <label for="fetchmail_issue"/>
                        <button name="configure_fetchmail_issue" type="object" string="Configure" icon="gtk-go-forward"
                            attrs="{'invisible': [('fetchmail_issue','=',False)]}" class="oe_link"/>
                    </div>
                </div>
            </field>
        </record>

    </data>
</openerp>