Be explicit about subdomain_ and maindomain_ urls in plugins

src/pretix/plugins/paypal/urls.py

@@ -1,10 +0,0 @@
-from django.conf.urls import include, url
-
-from .views import abort, success
-
-urlpatterns = [
-    url(r'^(?:(?P<organizer>[^/]+)/)?(?P<event>[^/]+)/paypal/', include([
-        url(r'^abort/$', abort, name='abort'),
-        url(r'^return/$', success, name='return'),
-    ])),
-]