PayPal: Migrate to Order v2 API and ISU authentication (#2493)

Co-authored-by: Raphael Michel <michel@rami.io>

src/pretix/base/models/event.py

@@ -700,8 +700,8 @@ class Event(EventMixin, LoggedModel):
 
         from ..signals import event_copy_data
         from . import (
-            Discount, Item, ItemAddOn, ItemBundle, ItemCategory, ItemMetaValue, Question,
-            Quota,
+            Discount, Item, ItemAddOn, ItemBundle, ItemCategory, ItemMetaValue,
+            Question, Quota,
         )
 
         #  Note: avoid self.set_active_plugins(), it causes trouble e.g. for the badges plugin.