trivial: update management command exception syntax for python 3 (#41651)

corbo/management/commands/sync_external_feeds.py

@@ -28,6 +28,6 @@ class Command(BaseCommand):
         for category in Category.objects.filter(rss_feed_url__isnull=False):
             try:
                 category.save()
-            except Exception, e:
+            except Exception as e:
                 logger.warning('Error occured while synchronizing feeds from %s: %s',
                                category, e)