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/plugins/statistics/signals.py

@@ -1,5 +1,5 @@
-from django.core.urlresolvers import resolve, reverse
 from django.dispatch import receiver
+from django.urls import resolve, reverse
 from django.utils.translation import ugettext_lazy as _
 
 from pretix.base.signals import order_paid, order_placed

src/pretix/plugins/statistics/templates/pretixplugins/statistics/index.html

@@ -1,7 +1,7 @@
 {% extends "pretixcontrol/event/base.html" %}
 {% load i18n %}
 {% load compress %}
-{% load staticfiles %}
+{% load static %}
 {% load escapejson %}
 {% block title %}{% trans "Statistics" %}{% endblock %}
 {% block content %}