Fixed #21734 -- Handled ProtectedError in a POST to admin's delete_selected action.

django/contrib/admin/actions.py

@@ -38,7 +38,7 @@ def delete_selected(modeladmin, request, queryset):
 
     # The user has already confirmed the deletion.
     # Do the deletion and return a None to display the change list view again.
-    if request.POST.get('post'):
+    if request.POST.get('post') and not protected:
         if perms_needed:
             raise PermissionDenied
         n = queryset.count()

tests/admin_views/tests.py

@@ -3123,6 +3123,8 @@ class AdminActionsTest(TestCase):
             'action': 'delete_selected',
             'index': 0,
         }
+        delete_confirmation_data = action_data.copy()
+        delete_confirmation_data['post'] = 'yes'
 
         response = self.client.post(reverse('admin:admin_views_question_changelist'), action_data)
 
@@ -3138,6 +3140,12 @@ class AdminActionsTest(TestCase):
             html=True
         )
 
+        # A POST request to delete protected objects should display the page
+        # which says the deletion is prohibited.
+        response = self.client.post(reverse('admin:admin_views_question_changelist'), delete_confirmation_data)
+        self.assertContains(response, "would require deleting the following protected related objects")
+        self.assertEqual(Question.objects.count(), 2)
+
     def test_model_admin_default_delete_action_no_change_url(self):
         """
         Default delete action shouldn't break if a user's ModelAdmin removes the url for change_view.