report_product_variant/views/producto_variant tree.xml

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

    <record id="product_sin_variant1"  model="ir.actions.act_window">
        <field name="name">Producto sin Variantes</field>
        <field name="res_model">product.template</field>
        <field name="view_type">form</field>
        <field name="view_mode">tree</field>
    </record>


    <record id="product_sin_variant_tree" model="ir.ui.view">
            <field name="name">product.sin.variant.tree</field>
            <field name="model">product.template</field>
            <field name="view_type">tree</field>
            <field name="arch" type="xml">
                <tree ditable='bottom' delete='false' create='false'>
                  <field name="name"/>
                  <field name="product_variant_count"/>
                </tree>
            </field>
      </record>



    <menuitem id="menu_product_sin_variant" name="Product sin Variantes" parent="base.next_id_64"/>
    <menuitem id="submenu_product_sin_variant" name="producto sim Variantes " action="product_sin_variant1"
              parent="menu_product_sin_variant" />

  </data>
</openerp>