Finish implementation of changing payment method

aleksis/apps/tezor/templates/tezor/invoice/full.html

@@ -75,7 +75,7 @@
                   <td>
                     <select name="variant" {% if not can_change_variant %}disabled{% endif %}>
                       {% for choice in object.get_variant_choices %}
-                        <option value="{{ choice.0 }}" {% if object.get_variant_name == choice.0 %}selected{% endif %}>{{ choice.1 }}</option>
+                        <option value="{{ choice.0 }}" {% if object.variant == choice.0 %}selected{% endif %}>{{ choice.1 }}</option>
                       {% endfor %}
                     </select>
                   </td>

aleksis/apps/tezor/views.py

 from django.conf import settings
+from django.core.exceptions import PermissionDenied, SuspiciousOperation
+from django.http import HttpResponseBadRequest
 from django.shortcuts import get_object_or_404, redirect, render
 from django.urls import reverse_lazy
 from django.utils.decorators import method_decorator
@@ -45,14 +47,14 @@ class DoPaymentView(PermissionRequiredMixin, View):
 
         new_variant = request.GET.get("variant", None)
         if new_variant:
-            if xxx_has_perm("tezor.change_payment_variant", self.object):  # FIXME
-                if variant in settings.PAYMENT_VARIANTS:
-                    object.variant = variant
-                    object.save()
+            if request.user.has_perm("tezor.change_payment_variant", self.object):
+                if new_variant in settings.PAYMENT_VARIANTS:
+                    self.object.variant = new_variant
+                    self.object.save()
                 else:
-                    raise xxxbadrequest  # FIXME
+                    raise SuspiciousOperation()
             else:
-                raise permissiondenied  # FIXME
+                raise PermissionDenied()
 
         if self.object.status not in [
             PaymentStatus.WAITING,