'First step of ExpressCheckout. Redirect the request to PayPal using the
data returned from setExpressCheckout.'

def redirect_to_express(self):

    wpp = PayPalWPP(self.request)
    nvp_obj = wpp.setExpressCheckout(self.item)
    if (not nvp_obj.flag):
        pp_params = dict(token=nvp_obj.token, AMT=self.item['amt'], RETURNURL=self.item['returnurl'], CANCELURL=self.item['cancelurl'])
        pp_url = (self.get_endpoint() % urlencode(pp_params))
        return HttpResponseRedirect(pp_url)
    else:
        self.context['errors'] = self.errors['paypal']
        return self.render_payment_form()
