Integrate django-scopes (#1319)

* Install django-scopes

* Fix tests.api

* Update tasks and cronjobs

* Fix remaining tests

* Remove unused import

* Fix tests after rebase

* Disable scopes for get_Events_with_any_permission

* Disable scopes for a management command

src/tests/base/test_notifications.py

@@ -5,6 +5,7 @@ import pytest
 from django.core import mail as djmail
 from django.db import transaction
 from django.utils.timezone import now
+from django_scopes import scope
 
 from pretix.base.models import (
     Event, Item, Order, OrderPosition, Organizer, User,
@@ -18,7 +19,8 @@ def event():
         organizer=o, name='Dummy', slug='dummy',
         date_from=now()
     )
-    return event
+    with scope(organizer=o):
+        yield event
 
 
 @pytest.fixture