I need to redirect the user to another site the user clicks on a specific button.

I'm trying doing this like described as below. But is does not work.

When the program reaches on the method index from the VrtxEvents controller, the system redirect the request to the location http://localhost:8069/www.gmail.com.

But the expected behavior is it redirect to the location www.gmail.com. 

My view

<record model="ir.ui.view" id="vrtx_view_event_tree">
<field name="name">event.event.tree</field>
<field name="model">event.event</field>
<field name="arch" type="xml">
    <tree string="Events" create="false" edit="false" delete="false">
        <field name="name" string="Name"/>
        <field name="date_begin"/>
        <field name="date_end"/>
        <field name="state"/>
        <button string="Click Here" name="pagseguro"  type="object"/>
    </tree>
</field>

My model

class Event(models.Model):
    _inherit = "event.event"
    @api.multi
    def pagseguro(self):
        return {
            "url": "/vrtx_events/vrtx_events/",
            "type": "ir.actions.act_url"
        }

My controller class:

from openerp import http
from werkzeug.utils import redirect

class VrtxEvents(http.Controller):
    @http.route('/vrtx_events/vrtx_events/', auth='public')
    def index(self, **kw):
        response = redirect("www.gmail.com")
        return response