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/templates/pretixcontrol/user/2fa_confirm_u2f.html

@@ -1,7 +1,7 @@
 {% extends "pretixcontrol/base.html" %}
 {% load i18n %}
 {% load bootstrap3 %}
-{% load staticfiles %}
+{% load static %}
 {% load compress %}
 {% block title %}{% trans "Add a two-factor authentication device" %}{% endblock %}
 {% block content %}

src/pretix/control/templates/pretixcontrol/user/reauth.html

@@ -2,7 +2,7 @@
 {% load i18n %}
 {% load bootstrap3 %}
 {% load compress %}
-{% load staticfiles %}
+{% load static %}
 {% block content %}
     <form class="form-signin" id="u2f-form" action="" method="post">
         {% csrf_token %}