Upgrade to Django 2.1 (#710)

* Upgrade to Django 2.0

* more models

* i18n foo

* Update setup.py

* Fix Sentry exception PRETIXEU-JC

* Enforce slug uniqueness

* Import sorting

* Upgrade to Django 2.1

* Travis config

* Try to fix PostgreSQL failure

* Smaller test matrix

* staticfiles→static

* Include request in all authenticate() calls

src/pretix/control/views/event.py

@@ -9,7 +9,6 @@ from django.conf import settings
 from django.contrib import messages
 from django.contrib.contenttypes.models import ContentType
 from django.core.files import File
-from django.core.urlresolvers import reverse
 from django.db import transaction
 from django.db.models import ProtectedError
 from django.http import (
@@ -17,6 +16,7 @@ from django.http import (
     JsonResponse,
 )
 from django.shortcuts import get_object_or_404, redirect
+from django.urls import reverse
 from django.utils import translation
 from django.utils.formats import date_format
 from django.utils.functional import cached_property