fix: empty basket for new user

ecommerce/coupons/views.py

@@ -169,20 +169,27 @@ def get(self, request):  # pylint: disable=too-many-statements
         if not sku:
             return render(request, template_name, {'error': _('SKU not provided.')})
 
+        try:
+            product = StockRecord.objects.get(partner_sku=sku).product
+        except StockRecord.DoesNotExist:
+            return render(request, template_name, {'error': _('The product does not exist.')})
+
         try:
             voucher = Voucher.objects.get(code=code)
         except Voucher.DoesNotExist:
+            try:
+                basket = prepare_basket(request, [product])
+            except AlreadyPlacedOrderException:
+                msg = _('You have already purchased {course} seat.').format(course=product.course.name)
+                return render(request, template_name, {'error': msg})
+
             msg = 'No voucher found with code {code}'.format(code=code)
             messages.error(self.request, _(msg))
+
             redirect_url = get_payment_microfrontend_or_basket_url(self.request) + "?coupon_redeem_redirect=1"
             redirect_url = add_stripe_flag_to_url(redirect_url, self.request)
             return HttpResponseRedirect(redirect_url)
 
-        try:
-            product = StockRecord.objects.get(partner_sku=sku).product
-        except StockRecord.DoesNotExist:
-            return render(request, template_name, {'error': _('The product does not exist.')})
-
         valid_voucher, msg, hide_error_message = voucher_is_valid(voucher, [product], request)
         if not valid_voucher:
             logger.warning('[Code Redemption Failure] The voucher is not valid for this product. '