Improve performance by not re-evaluating main context processors on

every template rendering in a signal receiver

src/pretix/base/migrations/0149_order_cancellation_date.py

@@ -1,7 +1,7 @@
 # Generated by Django 3.0.4 on 2020-03-25 14:40
 
 from django.db import migrations, models
-from django.db.models import OuterRef, Count, Subquery, Q
+from django.db.models import Count, OuterRef, Q, Subquery
 from django.utils.timezone import now