Update django to 2.1.1

[pyup-bot]

This PR updates Django from 2.1 to 2.1.1.

Changelog

2.1.1

==========================

*August 31, 2018*

Django 2.1.1 fixes several bugs in 2.1.

Bugfixes
========

* Fixed a race condition in ``QuerySet.update_or_create()`` that could result
in data loss (:ticket:`29499`).

* Fixed a regression where ``QueryDict.urlencode()`` crashed if the dictionary
contains a non-string value (:ticket:`29627`).

* Fixed a regression in Django 2.0 where using ``manage.py test --keepdb``
fails on PostgreSQL if the database exists and the user doesn't have
permission to create databases (:ticket:`29613`).

* Fixed a regression in Django 2.0 where combining ``Q`` objects with ``__in``
lookups and lists crashed (:ticket:`29643`).

* Fixed translation failure of ``DurationField``'s "overflow" error message
(:ticket:`29623`).

* Fixed a regression where the admin change form crashed if the user doesn't
have the 'add' permission to a model that uses ``TabularInline``
(:ticket:`29637`).

* Fixed a regression where a ``related_query_name`` reverse accessor wasn't set
up when a ``GenericRelation`` is declared on an abstract base model
(:ticket:`29653`).

* Fixed the test client's JSON serialization of a request data dictionary for
structured content type suffixes (:ticket:`29662`).

* Made the admin change view redirect to the changelist view after a POST if
the user has the 'view' permission (:ticket:`29663`).

* Fixed admin change view crash for view-only users if the form has an extra
form field (:ticket:`29682`).

* Fixed a regression in Django 2.0.5 where ``QuerySet.values()`` or
``values_list()`` after combining querysets with ``extra()`` with
``union()``, ``difference()``, or ``intersection()`` crashed due to
mismatching columns (:ticket:`29694`).

* Fixed crash if ``InlineModelAdmin.has_add_permission()`` doesn't accept the
``obj`` argument (:ticket:`29723`).


========================

Links

• PyPI: https://pypi.org/project/django
• Changelog: https://pyup.io/changelogs/django/
• Homepage: https://www.djangoproject.com/

[coveralls]

Coverage remained the same at 87.846% when pulling 2ebb30b on pyup-update-django-2.1-to-2.1.1 into 056e637 on master.