django/docs/releases/1.11.txt

=============================================
Django 1.11 release notes - UNDER DEVELOPMENT
=============================================

Welcome to Django 1.11!

These release notes cover the :ref:`new features <whats-new-1.11>`, as well as
some :ref:`backwards incompatible changes <backwards-incompatible-1.11>` you'll
want to be aware of when upgrading from Django 1.10 or older versions. We've
:ref:`begun the deprecation process for some features
<deprecated-features-1.11>`.

See the :doc:`/howto/upgrade-version` guide if you're updating an existing
project.

Django 1.11 is designated as a :term:`long-term support release`. It will
receive security updates for at least three years after its release. Support
for the previous LTS, Django 1.8, will end in April 2018.

Python compatibility
====================

Like Django 1.10, Django 1.11 requires Python 2.7, 3.4, or 3.5. We **highly
recommend** and only officially support the latest release of each series.

The Django 1.11.x series is the last to support Python 2. The next major
release, Django 2.0, will only support Python 3.5+.

Deprecating warnings are no longer loud by default
==================================================

Unlike older versions of Django, Django's own deprecation warnings are no
longer displayed by default. This is consistent with Python's default behavior.

This change allows third-party apps to support both Django 1.11 LTS and Django
1.8 LTS without having to add code to avoid deprecation warnings.

Following the release of Django 2.0, we suggest that third-party app authors
drop support for all versions of Django prior to 1.11. At that time, you should
be able run your package's tests using ``python -Wd`` so that deprecation
warnings do appear. After making the deprecation warning fixes, your app should
be compatible with Django 2.0.

.. _whats-new-1.11:

What's new in Django 1.11
=========================

Class-based model indexes
-------------------------

The new :mod:`django.db.models.indexes` module contains classes which ease
creating database indexes. Indexes are added to models using the
:attr:`Meta.indexes <django.db.models.Options.indexes>` option.

The :class:`~django.db.models.Index` class creates a b-tree index, as if you
used :attr:`~django.db.models.Field.db_index` on the model field or
:attr:`~django.db.models.Options.index_together` on the model ``Meta`` class.
It can be subclassed to support different index types, such as
:class:`~django.contrib.postgres.indexes.GinIndex`. It also allows defining the
order (ASC/DESC) for the columns of the index.

Minor features
--------------

:mod:`django.contrib.admin`
~~~~~~~~~~~~~~~~~~~~~~~~~~~

* :attr:`.ModelAdmin.date_hierarchy` can now reference fields across relations.

* The new :meth:`ModelAdmin.get_exclude()
  <django.contrib.admin.ModelAdmin.get_exclude>` hook allows specifying the
  exclude fields based on the request or model instance.

:mod:`django.contrib.admindocs`
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

* ...

:mod:`django.contrib.auth`
~~~~~~~~~~~~~~~~~~~~~~~~~~

* The default iteration count for the PBKDF2 password hasher is increased by
  20%.

* The :class:`~django.contrib.auth.views.LoginView` and
  :class:`~django.contrib.auth.views.LogoutView` class-based views supersede the
  deprecated ``login()`` and ``logout()`` function-based views.

* The :class:`~django.contrib.auth.views.PasswordChangeView`,
  :class:`~django.contrib.auth.views.PasswordChangeDoneView`,
  :class:`~django.contrib.auth.views.PasswordResetView`,
  :class:`~django.contrib.auth.views.PasswordResetDoneView`,
  :class:`~django.contrib.auth.views.PasswordResetConfirmView`, and
  :class:`~django.contrib.auth.views.PasswordResetCompleteView` class-based
  views supersede the deprecated ``password_change()``,
  ``password_change_done()``, ``password_reset()``, ``password_reset_done()``,
  ``password_reset_confirm()``, and ``password_reset_complete()`` function-based
  views.

* The new ``post_reset_login`` attribute for
  :class:`~django.contrib.auth.views.PasswordResetConfirmView` allows
  automatically logging in a user after a successful password reset.

* :func:`~django.contrib.auth.update_session_auth_hash` now rotates the session
  key to allow a password change to invalidate stolen session cookies.

* The new ``success_url_allowed_hosts`` attribute for
  :class:`~django.contrib.auth.views.LoginView` and
  :class:`~django.contrib.auth.views.LogoutView` allows specifying a set of
  hosts that are safe for redirecting after login and logout.

* Added password validators ``help_text`` to
  :class:`~django.contrib.auth.forms.UserCreationForm`.

* The ``HttpRequest`` is now passed to :func:`~django.contrib.auth.authenticate`
  which in turn passes it to the authentication backend if it accepts a
  ``request`` argument.

* The :func:`~django.contrib.auth.signals.user_login_failed` signal now
  receives a ``request`` argument.

* :class:`~django.contrib.auth.forms.PasswordResetForm` supports custom user
  models that use an email field named something other than ``'email'``.
  Set :attr:`CustomUser.EMAIL_FIELD
  <django.contrib.auth.models.CustomUser.EMAIL_FIELD>` to the name of the field.

:mod:`django.contrib.contenttypes`
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

* When stale content types are detected in the
  :djadmin:`remove_stale_contenttypes` command, there's now a list of related
  objects such as ``auth.Permission``\s that will also be deleted. Previously,
  only the content types were listed (and this prompt was after ``migrate``
  rather than in a separate command).

:mod:`django.contrib.gis`
~~~~~~~~~~~~~~~~~~~~~~~~~

* The new :meth:`.GEOSGeometry.from_gml` and :meth:`.OGRGeometry.from_gml`
  methods allow creating geometries from GML.

* Added support for the :lookup:`dwithin` lookup on SpatiaLite.

* The OpenLayers-based form widgets now use ``OpenLayers.js`` from
  ``https://cdnjs.cloudflare.com`` which is more suitable for production use
  than the the old ``http://openlayers.org`` source.

* PostGIS migrations can now change field dimensions.

:mod:`django.contrib.messages`
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

* ...

:mod:`django.contrib.postgres`
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

* The new ``distinct`` argument for
  :class:`~django.contrib.postgres.aggregates.StringAgg` determines if
  concatenated values will be distinct.

* The new :class:`~django.contrib.postgres.indexes.GinIndex` class allows
  creating gin indexes in the database.

* :class:`~django.contrib.postgres.fields.JSONField` accepts a new ``encoder``
  parameter to specify a custom class to encode data types not supported by the
  standard encoder.

* The new :class:`~django.contrib.postgres.fields.CITextField` and
  :class:`~django.contrib.postgres.operations.CITextExtension` migration
  operation allow using PostgreSQL's ``citext`` extension for case-insensitive
  lookups.

* The new :class:`~django.contrib.postgres.aggregates.JsonAgg` allows
  aggregating values as a JSON array.

:mod:`django.contrib.redirects`
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

* ...

:mod:`django.contrib.sessions`
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

* ...

:mod:`django.contrib.sitemaps`
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

* ...

:mod:`django.contrib.sites`
~~~~~~~~~~~~~~~~~~~~~~~~~~~

* ...

:mod:`django.contrib.staticfiles`
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

* ...

:mod:`django.contrib.syndication`
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

* ...

Cache
~~~~~

* Memcached backends now pass the contents of :setting:`OPTIONS <CACHES-OPTIONS>`
  as keyword arguments to the client constructors, allowing for more advanced
  control of client behavior. See the :ref:`cache arguments <cache_arguments>`
  documentation for examples.

* Memcached backends now allow defining multiple servers as a comma-delimited
  string in :setting:`LOCATION <CACHES-LOCATION>`, for convenience with
  third-party services that use such strings in environment variables.

CSRF
~~~~

* ...

Database backends
~~~~~~~~~~~~~~~~~

* Added the ``skip_locked`` argument to :meth:`.QuerySet.select_for_update()`
  on PostgreSQL 9.5+ and Oracle to execute queries with
  ``FOR UPDATE SKIP LOCKED``.

* Added the :setting:`TEST['TEMPLATE'] <TEST_TEMPLATE>` setting to let
  PostgreSQL users specify a template for creating the test database.

Email
~~~~~

* Added the :setting:`EMAIL_USE_LOCALTIME` setting to allow sending SMTP date
  headers in the local time zone rather than in UTC.

* ``EmailMessage.attach()`` and ``attach_file()`` now fall back to MIME type
  ``application/octet-stream`` when binary content that can't be decoded as
  UTF-8 is specified for a ``text/*`` attachment.

File Storage
~~~~~~~~~~~~

* To make it wrappable by :class:`io.TextIOWrapper`,
  :class:`~django.core.files.File` now has the ``readable()``, ``writable()``,
  and ``seekable()`` methods.

File Uploads
~~~~~~~~~~~~

* ...

Forms
~~~~~

* The new :attr:`CharField.empty_value <django.forms.CharField.empty_value>`
  attribute allows specifying the Python value to use to represent "empty".

* The new :meth:`Form.get_initial_for_field()
  <django.forms.Form.get_initial_for_field>` method returns initial data for a
  form field.

Generic Views
~~~~~~~~~~~~~

* ...

Internationalization
~~~~~~~~~~~~~~~~~~~~

* Number formatting and the :setting:`NUMBER_GROUPING` setting support
  non-uniform digit grouping.

Management Commands
~~~~~~~~~~~~~~~~~~~

* The new :option:`loaddata --exclude` option allows excluding models and apps
  while loading data from fixtures.

* The unused ``BaseCommand.can_import_settings`` attribute is removed.

Migrations
~~~~~~~~~~

* ...

Models
~~~~~~

* Added support for callable values in the ``defaults`` argument of
  :meth:`QuerySet.update_or_create()
  <django.db.models.query.QuerySet.update_or_create>` and
  :meth:`~django.db.models.query.QuerySet.get_or_create`.

* :class:`~django.db.models.ImageField` now has a default
  :data:`~django.core.validators.validate_image_file_extension` validator.

* Added support for time truncation to
  :class:`~django.db.models.functions.datetime.Trunc` functions.

* Added the :class:`~django.db.models.functions.datetime.TruncTime` function
  to truncate :class:`~django.db.models.DateTimeField` to its time component
  and exposed it through the :lookup:`time` lookup.

* Added support for expressions in :meth:`.QuerySet.values` and
  :meth:`~.QuerySet.values_list`.

* Added support for query expressions on lookups that take multiple arguments,
  such as ``range``.

* You can now use the ``unique=True`` option with
  :class:`~django.db.models.FileField`.

Requests and Responses
~~~~~~~~~~~~~~~~~~~~~~

* Added :meth:`QueryDict.fromkeys() <django.http.QueryDict.fromkeys>`.

* :class:`~django.middleware.common.CommonMiddleware` now sets the
  ``Content-Length`` response header for non-streaming responses.

* Added the :setting:`SECURE_HSTS_PRELOAD` setting to allow appending the
  ``preload`` directive to the ``Strict-Transport-Security`` header.

* :class:`~django.middleware.http.ConditionalGetMiddleware` now adds the
  ``ETag`` header to responses.

Serialization
~~~~~~~~~~~~~

* The new ``django.core.serializers.base.Serializer.stream_class`` attribute
  allows subclasses to customize the default stream.

* The encoder used by the :ref:`JSON serializer <serialization-formats-json>`
  can now be customized by passing a ``cls`` keyword argument to the
  ``serializers.serialize()`` function.

* :class:`~django.core.serializers.json.DjangoJSONEncoder` now serializes
  :class:`~datetime.timedelta` objects (used by
  :class:`~django.db.models.DurationField`).

Signals
~~~~~~~

* ...

Templates
~~~~~~~~~

* :meth:`~django.utils.safestring.mark_safe` can now be used as a decorator.

* The :class:`~django.template.backends.jinja2.Jinja2` template backend now
  supports context processors by setting the ``'context_processors'`` option in
  :setting:`OPTIONS <TEMPLATES-OPTIONS>`.

* The :ttag:`regroup` tag now returns ``namedtuple``\s instead of dictionaries
  so you can unpack the group object directly in a loop, e.g.
  ``{% for grouper, list in regrouped %}``.

* Added a :ttag:`resetcycle` template tag to allow resetting the sequence of
  the :ttag:`cycle` template tag.

Tests
~~~~~

* Added :meth:`.DiscoverRunner.get_test_runner_kwargs` to allow customizing the
  keyword arguments passed to the test runner.

* Added the :option:`test --debug-mode` option to help troubleshoot test
  failures by setting the :setting:`DEBUG` setting to ``True``.

* The new :func:`django.test.utils.setup_databases` (moved from
  ``django.test.runner``) and :func:`~django.test.utils.teardown_databases`
  functions make it easier to build custom test runners.

* Added support for :meth:`python:unittest.TestCase.subTest`’s when using the
  :option:`test --parallel` option.

URLs
~~~~

* ...

Validators
~~~~~~~~~~

* Added :class:`~django.core.validators.FileExtensionValidator` to validate
  file extensions and
  :data:`~django.core.validators.validate_image_file_extension` to validate
  image files.

.. _backwards-incompatible-1.11:

Backwards incompatible changes in 1.11
======================================

:mod:`django.contrib.gis`
-------------------------

* To simplify the codebase and because it's easier to install than when
  ``contrib.gis`` was first released, :ref:`gdalbuild` is now a required
  dependency for GeoDjango. In older versions, it's only required for SQLite.

* ``contrib.gis.maps`` is removed as it interfaces with a retired version of
  the Google Maps API and seems to be unmaintained. If you're using it, `let
  us know <https://code.djangoproject.com/ticket/14284>`_.

Database backend API
--------------------

* The ``DatabaseOperations.time_trunc_sql()`` method is added to support
  ``TimeField`` truncation. It accepts a ``lookup_type`` and ``field_name``
  arguments and returns the appropriate SQL to truncate the given time field
  ``field_name`` to a time object with only the given specificity. The
  ``lookup_type`` argument can be either ``'hour'``, ``'minute'``, or
  ``'second'``.

* The ``DatabaseOperations.datetime_cast_time_sql()`` method is added to
  support the :lookup:`time` lookup. It accepts a ``field_name`` and ``tzname``
  arguments and returns the SQL necessary to cast a datetime value to time value.

* To enable ``FOR UPDATE SKIP LOCKED`` support, set
  ``DatabaseFeatures.has_select_for_update_skip_locked = True``.

* The new ``DatabaseFeatures.supports_index_column_ordering`` attribute
  specifies if a database allows defining ordering for columns in indexes. The
  default value is ``True`` and the ``DatabaseIntrospection.get_constraints()``
  method should include an ``'orders'`` key in each of the returned
  dictionaries with a list of ``'ASC'`` and/or ``'DESC'`` values corresponding
  to the the ordering of each column in the index.

* :djadmin:`inspectdb` no longer calls ``DatabaseIntrospection.get_indexes()``
  which is deprecated. Custom database backends should ensure all types of
  indexes are returned by ``DatabaseIntrospection.get_constraints()``.

Dropped support for PostgreSQL 9.2 and PostGIS 2.0
--------------------------------------------------

Upstream support for PostgreSQL 9.2 ends in September 2017. As a consequence,
Django 1.11 sets PostgreSQL 9.3 as the minimum version it officially supports.

Support for PostGIS 2.0 is also removed as PostgreSQL 9.2 is the last version
to support it.

``LiveServerTestCase`` binds to port zero
-----------------------------------------

Rather than taking a port range and iterating to find a free port,
``LiveServerTestCase`` binds to port zero and relies on the operating system
to assign a free port. The ``DJANGO_LIVE_TEST_SERVER_ADDRESS`` environment
variable is no longer used, and as it's also no longer used, the
``manage.py test --liveserver`` option is removed.

Protection against insecure redirects in :mod:`django.contrib.auth` and ``i18n`` views
--------------------------------------------------------------------------------------

``LoginView``, ``LogoutView`` (and the deprecated function-based equivalents),
and :func:`~django.views.i18n.set_language` protect users from being redirected
to non-HTTPS ``next`` URLs when the app is running over HTTPS.

``QuerySet.get_or_create()`` and ``update_or_create()`` validate arguments
--------------------------------------------------------------------------

To prevent typos from passing silently,
:meth:`~django.db.models.query.QuerySet.get_or_create` and
:meth:`~django.db.models.query.QuerySet.update_or_create` check that their
arguments are model fields. This should be backwards-incompatible only in the
fact that it might expose a bug in your project.

``pytz`` is a required dependency and support for ``settings.TIME_ZONE = None`` is removed
------------------------------------------------------------------------------------------

To simplify Django's timezone handling, ``pytz`` is now a required dependency.
It's automatically installed along with Django.

Support for ``settings.TIME_ZONE = None`` is removed as the behavior isn't
commonly used and is questionably useful. If you want to automatically detect
the timezone based on the system timezone, you can use `tzlocal
<https://pypi.python.org/pypi/tzlocal>`_::

    from tzlocal import get_localzone

    TIME_ZONE = get_localzone().zone

This works similar to ``settings.TIME_ZONE = None`` except that it also sets
``os.environ['TZ']``. `Let us know
<https://groups.google.com/d/topic/django-developers/OAV3FChfuPM/discussion>`__
if there's a use case where you find you can't adapt your code to set a
``TIME_ZONE``.

Miscellaneous
-------------

* If no items in the feed have a ``pubdate`` or ``updateddate`` attribute,
  :meth:`SyndicationFeed.latest_post_date()
  <django.utils.feedgenerator.SyndicationFeed.latest_post_date>` now returns
  the current UTC date/time, instead of a datetime without any timezone
  information.

* Support for SpatiaLite < 4.0 is dropped.

* CSRF failures are logged to the ``django.security.csrf`` logger instead of
  ``django.request``.

* :setting:`ALLOWED_HOSTS` validation is no longer disabled when running tests.
  If your application includes tests with custom host names, you must include
  those host names in :setting:`ALLOWED_HOSTS`. See
  :ref:`topics-testing-advanced-multiple-hosts`.

* Using a foreign key's id (e.g. ``'field_id'``) in ``ModelAdmin.list_display``
  displays the related object's ID. Remove the ``_id`` suffix if you want the
  old behavior of the string representation of the object.

* In model forms, :class:`~django.db.models.CharField` with ``null=True`` now
  saves ``NULL`` for blank values instead of empty strings.

* On Oracle, :meth:`Model.validate_unique()
  <django.db.models.Model.validate_unique>` no longer checks empty strings for
  uniqueness as the database interprets the value as ``NULL``.

* If you subclass :class:`.AbstractUser` and override ``clean()``, be sure it
  calls ``super()``. :meth:`.BaseUserManager.normalize_email` is called in a
  new :meth:`.AbstractUser.clean` method so that normalization is applied in
  cases like model form validation.

* ``EmailField`` and ``URLField`` no longer accept the ``strip`` keyword
  argument. Remove it because it doesn't have an effect in older versions of
  Django as these fields alway strip whitespace.

* The ``checked`` and ``selected`` attribute rendered by form widgets now uses
  HTML5 boolean syntax rather than XHTML's ``checked='checked'`` and
  ``selected='selected'``.

* :meth:`RelatedManager.add()
  <django.db.models.fields.related.RelatedManager.add>`,
  :meth:`~django.db.models.fields.related.RelatedManager.remove`,
  :meth:`~django.db.models.fields.related.RelatedManager.clear`, and
  :meth:`~django.db.models.fields.related.RelatedManager.set` now
  clear the ``prefetch_related()`` cache.

* To prevent possible loss of saved settings,
  :func:`~django.test.utils.setup_test_environment` now raises an exception if
  called a second time before calling
  :func:`~django.test.utils.teardown_test_environment`.

* The undocumented ``DateTimeAwareJSONEncoder`` alias for
  :class:`~django.core.serializers.json.DjangoJSONEncoder` (renamed in Django
  1.0) is removed.

* The :class:`cached template loader <django.template.loaders.cached.Loader>`
  is now enabled if :setting:`DEBUG` is ``False`` and
  :setting:`OPTIONS['loaders'] <TEMPLATES-OPTIONS>` isn't specified. This could
  be backwards-incompatible if you have some :ref:`template tags that aren't
  thread safe <template_tag_thread_safety>`.

* The prompt for stale content type deletion no longer occurs after running the
  ``migrate`` command. Use the new :djadmin:`remove_stale_contenttypes` command
  instead.

* The admin's widget for ``IntegerField`` uses ``type="number"`` rather than
  ``type="text"``.

* Conditional HTTP headers are now parsed and compared according to the
  :rfc:`7232` Conditional Requests specification rather than the older
  :rfc:`2616`.

* :func:`~django.utils.cache.patch_response_headers` no longer adds a
  ``Last-Modified`` header. According to the :rfc:`7234#section-4.2.2`, this
  header is useless alongside other caching headers that provide an explicit
  expiration time, e.g. ``Expires`` or ``Cache-Control``.
  :class:`~django.middleware.cache.UpdateCacheMiddleware` and
  :func:`~django.utils.cache.add_never_cache_headers` call
  ``patch_response_headers()`` and therefore are also affected by this change.

* In the admin templates, ``<p class="help">`` is replaced with a ``<div>`` tag
  to allow including lists inside help text.

* ``ConditionalGetMiddleware`` no longer sets the ``Date`` header as Web
  servers set that header.

* :meth:`~django.apps.AppConfig.get_model` and
  :meth:`~django.apps.AppConfig.get_models` now raise
  :exc:`~django.core.exceptions.AppRegistryNotReady` if they're called before
  models of all applications have been loaded. Previously they only required
  the target application's models to be loaded and thus could return models
  without all their relations set up. If you need the old behavior of
  ``get_model()``, set the ``require_ready`` argument to ``False``.

.. _deprecated-features-1.11:

Features deprecated in 1.11
===========================

``models.permalink()`` decorator
--------------------------------

Use :func:`django.urls.reverse` instead. For example::

    from django.db import models

    class MyModel(models.Model):
        ...

        @models.permalink
        def url(self):
            return ('guitarist_detail', [self.slug])

becomes::

    from django.db import models
    from django.urls import reverse

    class MyModel(models.Model):
        ...

        def url(self):
            return reverse('guitarist_detail', args=[self.slug])

Miscellaneous
-------------

* ``contrib.auth``’s ``login()`` and ``logout()`` function-based views are
  deprecated in favor of new class-based views
  :class:`~django.contrib.auth.views.LoginView` and
  :class:`~django.contrib.auth.views.LogoutView`.

* The unused ``extra_context`` parameter of
  ``contrib.auth.views.logout_then_login()``  is deprecated.

* ``contrib.auth``’s ``password_change()``, ``password_change_done()``,
  ``password_reset()``, ``password_reset_done()``, ``password_reset_confirm()``,
  and ``password_reset_complete()`` function-based views are deprecated in favor
  of new class-based views
  :class:`~django.contrib.auth.views.PasswordChangeView`,
  :class:`~django.contrib.auth.views.PasswordChangeDoneView`,
  :class:`~django.contrib.auth.views.PasswordResetView`,
  :class:`~django.contrib.auth.views.PasswordResetDoneView`,
  :class:`~django.contrib.auth.views.PasswordResetConfirmView`, and
  :class:`~django.contrib.auth.views.PasswordResetCompleteView`.

* ``django.test.runner.setup_databases()`` is moved to
  :func:`django.test.utils.setup_databases`. The old location is deprecated.

* ``django.utils.translation.string_concat()`` is deprecated in
  favor of :func:`django.utils.text.format_lazy`. ``string_concat(*strings)``
  can be replaced by ``format_lazy('{}' * len(strings), *strings)``.

* For the ``PyLibMCCache`` cache backend, passing ``pylibmc`` behavior settings
  as top-level attributes of ``OPTIONS`` is deprecated. Set them under a
  ``behaviors`` key within ``OPTIONS`` instead.

* The ``host`` parameter of ``django.utils.http.is_safe_url()`` is deprecated
  in favor of the new ``allowed_hosts`` parameter.

* Silencing exceptions raised while rendering the
  :ttag:`{% include %} <include>` template tag is deprecated as the behavior is
  often more confusing than helpful. In Django 2.1, the exception will be
  raised.

* ``DatabaseIntrospection.get_indexes()`` is deprecated in favor of
  ``DatabaseIntrospection.get_constraints()``.

* :func:`~django.contrib.auth.authenticate` now passes a ``request`` argument
  to the ``authenticate()`` method of authentication backends. Support for
  methods that don't accept ``request`` will be removed in Django 2.1.

* The ``USE_ETAGS`` setting is deprecated in favor of
  :class:`~django.middleware.http.ConditionalGetMiddleware` which now adds the
  ``ETag`` header to responses regardless of the setting. ``CommonMiddleware``
  and ``django.utils.cache.patch_response_headers()`` will no longer set ETags
  when the deprecation ends.