# Django 2.1.8.dev20190330215650 documentation

# Django 2.0 release notes

December 2, 2017

Welcome to Django 2.0!

These release notes cover the new features, as well as some backwards incompatible changes you'll want to be aware of when upgrading from Django 1.11 or earlier. We've dropped some features that have reached the end of their deprecation cycle, and we've begun the deprecation process for some features.

This release starts Django's use of a loose form of semantic versioning, but there aren't any major backwards incompatible changes that might be expected of a 2.0 release. Upgrading should be a similar amount of effort as past feature releases.

See the Upgrading Django to a newer version guide if you're updating an existing project.

## Python compatibility

Django 2.0 supports Python 3.4, 3.5, 3.6, and 3.7. 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 2.7.

Django 2.0 will be the last release series to support Python 3.4. If you plan a deployment of Python 3.4 beyond the end-of-life for Django 2.0 (April 2019), stick with Django 1.11 LTS (supported until April 2020) instead. Note, however, that the end-of-life for Python 3.4 is March 2019.

## Third-party library support for older version of Django

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 to 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.

## What's new in Django 2.0

### Simplified URL routing syntax

The new `django.urls.path()` function allows a simpler, more readable URL routing syntax. For example, this example from previous Django releases:

    url(r'^articles/(?P<year>[0-9]{4})/$', views.year_archive),

could be written as:

    path('articles/<int:year>/', views.year_archive),

The new syntax supports type coercion of URL parameters. In the example, the view will receive the `year` keyword argument as an integer rather than as a string. Also, the URLs that will match are slightly less constrained in the rewritten example. For example, the year 10000 will now match since the year integers aren't constrained to be exactly four digits long as they are in the regular expression.

The `django.conf.urls.url()` function from previous versions is now available as `django.urls.re_path()`. The old location remains for backwards compatibility, without an imminent deprecation. The old `django.conf.urls.include()` function is now importable from `django.urls` so you can use `from django.urls import include, path, re_path` in your URLconfs.

The URL dispatcher document is rewritten to feature the new syntax and provide more details.

### Mobile-friendly `contrib.admin`

The admin is now responsive and supports all major mobile devices. Older browsers may experience varying levels of graceful degradation.

### Window expressions

The new `Window` expression allows adding an `OVER` clause to querysets. You can use window functions and aggregate functions in the expression.

### Minor features

#### `django.contrib.admin`

- The new `ModelAdmin.autocomplete_fields` attribute and `ModelAdmin.get_autocomplete_fields()` method allow using a Select2 search widget for `ForeignKey` and `ManyToManyField`.

#### `django.contrib.auth`

- The default iteration count for the PBKDF2 password hasher is increased from 36,000 to 100,000.

#### `django.contrib.gis`

- Added MySQL support for the `AsGeoJSON` function, `GeoHash` function, `IsValid` function, `isvalid` lookup, and distance lookups.
- Added the `Azimuth` and `LineLocatePoint` functions, supported on PostGIS and SpatiaLite.
- Any `GEOSGeometry` imported from GeoJSON now has its SRID set.
- Added the `OSMWidget.default_zoom` attribute to customize the map's default zoom level.
- Made metadata readable and editable on rasters through the `metadata`, `info`, and `metadata` attributes.
- Allowed passing driver-specific creation options to `GDALRaster` objects using `papsz_options`.
- Allowed creating `GDALRaster` objects in GDAL's internal virtual filesystem. Rasters can now be created from and converted to binary data in-memory.
- The new `GDALBand.color_interp()` method returns the color interpretation for the band.

#### `django.contrib.postgres`

- The new `distinct` argument for `ArrayAgg` determines if concatenated values will be distinct.
- The new `RandomUUID` database function returns a version 4 UUID. It requires use of PostgreSQL's `pgcrypto` extension which can be activated using the new `CryptoExtension` migration operation.
- `django.contrib.postgres.indexes.GinIndex` now supports the `fastupdate` and `gin_pending_list_limit` parameters.
- The new `GistIndex` class allows creating `GiST` indexes in the database. The new `BtreeGistExtension` migration operation installs the `btree_gist` extension to add support for operator classes that aren't built-in.
- `inspectdb` can now introspect `JSONField` and various `RangeField`s (`django.contrib.postgres` must be in `INSTALLED_APPS`).

#### `django.contrib.sitemaps`

- Added the `protocol` keyword argument to the `GenericSitemap` constructor.

#### Cache

- `cache.set_many()` now returns a list of keys that failed to be inserted. For the built-in backends, failed inserts can only happen on memcached.

#### File Storage

- `File.open()` can be used as a context manager, e.g. `with file.open() as f:`.

#### Forms

- The new `date_attrs` and `time_attrs` arguments for `SplitDateTimeWidget` and `SplitHiddenDateTimeWidget` allow specifying different HTML attributes for the `DateInput` and `TimeInput` (or hidden) subwidgets.
- The new `Form.errors.get_json_data()` method returns form errors as a dictionary suitable for including in a JSON response.

#### Generic Views

- The new `ContextMixin.extra_context` attribute allows adding context in `View.as_view()`.

#### Management Commands

- `inspectdb` now translates MySQL's unsigned integer columns to `PositiveIntegerField` or `PositiveSmallIntegerField`.
- The new `makemessages --add-location` option controls the comment format in PO files.
- `loaddata` can now read from stdin.
- The new `diffsettings --output` option allows formatting the output in a unified diff format.
- On Oracle, `inspectdb` can now introspect `AutoField` if the column is created as an identity column.
- On MySQL, `dbshell` now supports client-side TLS certificates.

#### Migrations

- The new `squashmigrations --squashed-name` option allows naming the squashed migration.

#### Models

- The new `StrIndex` database function finds the starting index of a string inside another string.
- On Oracle, `AutoField` and `BigAutoField` are now created as identity columns.
- The new `chunk_size` parameter of `QuerySet.iterator()` controls the number of rows fetched by the Python database client when streaming results from the database. For databases that don't support server-side cursors, it controls the number of results Django fetches from the database adapter.
- `QuerySet.earliest()`, `QuerySet.latest()`, and `Meta.get_latest_by` now allow ordering by several fields.
- Added the `ExtractQuarter` function to extract the quarter from `DateField` and `DateTimeField`, and exposed it through the `quarter` lookup.
- Added the `TruncQuarter` function to truncate `DateField` and `DateTimeField` to the first day of a quarter.
- Added the `db_tablespace` parameter to class-based indexes.
- If the database supports a native duration field (Oracle and PostgreSQL), `Extract` now works with `DurationField`.
- Added the `of` argument to `QuerySet.select_for_update()`, supported on PostgreSQL and Oracle, to lock only rows from specific tables rather than all selected tables. It may be helpful particularly when `select_for_update()` is used in conjunction with `select_related()`.
- The new `field_name` parameter of `QuerySet.in_bulk()` allows fetching results based on any unique model field.
- `CursorWrapper.callproc()` now takes an optional dictionary of keyword parameters, if the backend supports this feature. Of Django's built-in backends, only Oracle supports it.
- The new `connection.execute_wrapper()` method allows installing wrappers around execution of database queries.
- The new `filter` argument for built-in aggregates allows adding different conditionals to multiple aggregations over the same fields or relations.
- Added support for expressions in `Meta.ordering`.
- The new `named` parameter of `QuerySet.values_list()` allows fetching results as named tuples.
- The new `FilteredRelation` class allows adding an `ON` clause to querysets.

#### Pagination

- Added `Paginator.get_page()` to provide the documented pattern of handling invalid page numbers.

#### Requests and Responses

- The `runserver` Web server supports HTTP 1.1.

#### Templates

- To increase the usefulness of `Engine.get_default()` in third-party apps, it now returns the first engine if multiple `DjangoTemplates` engines are configured in `TEMPLATES` rather than raising `ImproperlyConfigured`.
- Custom template tags may now accept keyword-only arguments.

#### Tests

- Added threading support to `LiveServerTestCase`.
- Added settings that allow customizing the test tablespace parameters for Oracle: `DATAFILE_SIZE`, `DATAFILE_TMP_SIZE`, `DATAFILE_EXTSIZE`, and `DATAFILE_TMP_EXTSIZE`.

#### Validators

- The new `ProhibitNullCharactersValidator` disallows the null character in the input of the `CharField` form field and its subclasses. Null character input was observed from vulnerability scanning tools. Most databases silently discard null characters, but psycopg2 2.7+ raises an exception when trying to save a null character to a char/text field with PostgreSQL.

## Backwards incompatible changes in 2.0

### Removed support for bytestrings in some places

To support native Python 2 strings, older Django versions had to accept both bytestrings and unicode strings. Now that Python 2 support is dropped, bytestrings should only be encountered around input/output boundaries (handling of binary fields or HTTP streams, for example). You might have to update your code to limit bytestring usage to a minimum, as Django no longer accepts bytestrings in certain code paths. Python's `-b` option may help detect that mistake in your code.

For example, `reverse()` now uses `str()` instead of `force_text()` to coerce the `args` and `kwargs` it receives, prior to their placement in the URL. For bytestrings, this creates a string with an undesired `b` prefix as well as additional quotes (`str(b'foo')` is `"b'foo'"`). To adapt, call `decode()` on the bytestring before passing it to `reverse()`.

### Database backend API

This section describes changes that may be needed in third-party database backends.

- The `DatabaseOperations.datetime_cast_date_sql()`, `datetime_cast_time_sql()`, `datetime_trunc_sql()`, `datetime_extract_sql()`, and `date_interval_sql()` methods now return only the SQL to perform the operation instead of SQL and a list of parameters.
- Third-party database backends should add a `DatabaseWrapper.display_name` attribute with the name of the database that your backend works with. Django may use it in various messages, such as in system checks.
- The first argument of `SchemaEditor._alter_column_type_sql()` is now `model` rather than `table`.
- The first argument of `SchemaEditor._create_index_name()` is now `table_name` rather than `model`.
- To enable `FOR UPDATE OF` support, set `DatabaseFeatures.has_select_for_update_of = True`. If the database requires that the arguments to `OF` be columns rather than tables, set `DatabaseFeatures.select_for_update_of_column = True`.
- To enable support for `Window` expressions, set `DatabaseFeatures.supports_over_clause` to `True`. You may need to customize the `DatabaseOperations.window_start_rows_start_end()` and/or `window_start_range_start_end()` methods.
- Third-party database backends should add a `DatabaseOperations.cast_char_field_without_max_length` attribute with the database data type that will be used in the `Cast` function for a `CharField` if the `max_length` argument isn't provided.
- The first argument of `DatabaseCreation._clone_test_db()` and `get_test_db_clone_settings()` is now `suffix` rather than `number` (in case you want to rename the signatures in your backend for consistency). `django.test` also now passes those values as strings rather than as integers.
- Third-party database backends should add a `DatabaseIntrospection.get_sequences()` method based on the stub in `BaseDatabaseIntrospection`.

### Dropped support for Oracle 11.2

The end of upstream support for Oracle 11.2 is Dec. 2020. Django 1.11 will be supported until April 2020 which almost reaches this date. Django 2.0 officially supports Oracle 12.1+.

### Default MySQL isolation level is read committed

MySQL's default isolation level, repeatable read, may cause data loss in typical Django usage. To prevent that and for consistency with other databases, the default isolation level is now read committed. You can use the `DATABASES` setting to use a different isolation level, if needed.

### `AbstractUser.last_name` `max_length` increased to 150

A migration for `django.contrib.auth.models.User.last_name` is included. If you have a custom user model inheriting from `AbstractUser`, you'll need to generate and apply a database migration for your user model.

If you want to preserve the 30 character limit for last names, use a custom form:

    from django.contrib.auth.forms import UserChangeForm

    class MyUserChangeForm(UserChangeForm):
        last_name = forms.CharField(max_length=30, required=False)

If you wish to keep this restriction in the admin when editing users, set `UserAdmin.form` to use this form:

    from django.contrib.auth.admin import UserAdmin
    from django.contrib.auth.models import User

    class MyUserAdmin(UserAdmin):
        form = MyUserChangeForm

    admin.site.unregister(User)
    admin.site.register(User, MyUserAdmin)

### `QuerySet.reverse()` and `last()` are prohibited after slicing

Calling `QuerySet.reverse()` or `last()` on a sliced queryset leads to unexpected results due to the slice being applied after reordering. This is now prohibited, e.g.:

    >>> Model.objects.all()[:2].reverse()
    Traceback (most recent call last):
    ...
    TypeError: Cannot reverse a query once a slice has been taken.

### Form fields no longer accept optional arguments as positional arguments

To help prevent runtime errors due to incorrect ordering of form field arguments, optional arguments of built-in form fields are no longer accepted as positional arguments. For example:

    forms.IntegerField(25, 10)

raises an exception and should be replaced with:

    forms.IntegerField(max_value=25, min_value=10)

### `call_command()` validates the options it receives

`call_command()` now validates that the argument parser of the command being called defines all of the options passed to `call_command()`.

For custom management commands that use options not created using `parser.add_argument()`, add a `stealth_options` attribute on the command:

    class MyCommand(BaseCommand):
        stealth_options = ('option_name', ...)

### Indexes no longer accept positional arguments

For example:

    models.Index(['headline', '-pub_date'], 'index_name')

raises an exception and should be replaced with:

    models.Index(fields=['headline', '-pub_date'], name='index_name')

### Foreign key constraints are now enabled on SQLite

This will appear as a backwards-incompatible change (`IntegrityError: FOREIGN KEY constraint failed`) if attempting to save an existing model instance that's violating a foreign key constraint.

Foreign keys are now created with `DEFERRABLE INITIALLY DEFERRED` instead of `DEFERRABLE IMMEDIATE`. Thus, tables may need to be rebuilt to recreate foreign keys with the new definition, particularly if you're using a pattern like this:

    from django.db import transaction

    with transaction.atomic():
        Book.objects.create(author_id=1)
        Author.objects.create(id=1)

If you don't recreate the foreign key as `DEFERRED`, the first `create()` would fail now that foreign key constraints are enforced.

Backup your database first! After upgrading to Django 2.0, you can then rebuild tables using a script similar to this:

    from django.apps import apps
    from django.db import connection

    for app in apps.get_app_configs():
        for model in app.get_models(include_auto_created=True):
            if model._meta.managed and not (model._meta.proxy or model._meta.swapped):
                for base in model.__bases__:
                    if hasattr(base, '_meta'):
                        base._meta.local_many_to_many = []
                model._meta.local_many_to_many = []
                with connection.schema_editor() as editor:
                    editor._remake_table(model)

This script hasn't received extensive testing and needs adaption for various cases such as multiple databases. Feel free to contribute improvements.

In addition, because of a table alteration limitation of SQLite, it's prohibited to perform `RenameModel` and `RenameField` operations on models or fields referenced by other models in a transaction. In order to allow migrations containing these operations to be applied, you must set the `Migration.atomic` attribute to `False`.

### Miscellaneous

- The `SessionAuthenticationMiddleware` class is removed. It provided no functionality since session authentication is unconditionally enabled in Django 1.10.

- The default HTTP error handlers (`handler404`, etc.) are now callables instead of dotted Python path strings. Django favors callable references since they provide better performance and debugging experience.

- `RedirectView` no longer silences `NoReverseMatch` if the `pattern_name` doesn't exist.

- When `USE_L10N` is off, `FloatField` and `DecimalField` now respect `DECIMAL_SEPARATOR` and `THOUSAND_SEPARATOR` during validation. For example, with the settings:

      USE_L10N = False
      USE_THOUSAND_SEPARATOR = True
      DECIMAL_SEPARATOR = ','
      THOUSAND_SEPARATOR = '.'

  an input of `"1.345"` is now converted to `1345` instead of `1.345`.

- Subclasses of `AbstractBaseUser` are no longer required to implement `get_short_name()` and `get_full_name()`. (The base implementations that raise `NotImplementedError` are removed.) `django.contrib.admin` uses these methods if implemented but doesn't require them. Third-party apps that use these methods may want to adopt a similar approach.

- The `FIRST_DAY_OF_WEEK` and `NUMBER_GROUPING` format settings are now kept as integers in JavaScript and JSON i18n view outputs.

- `assertNumQueries()` now ignores connection configuration queries. Previously, if a test opened a new database connection, those queries could be included as part of the `assertNumQueries()` count.

- The default size of the Oracle test tablespace is increased from 20M to 50M and the default autoextend size is increased from 10M to 25M.

- To improve performance when streaming large result sets from the database, `QuerySet.iterator()` now fetches 2000 rows at a time instead of 100. The old behavior can be restored using the `chunk_size` parameter. For example:

      Book.objects.iterator(chunk_size=100)

- Providing unknown package names in the `packages` argument of the `JavaScriptCatalog` view now raises `ValueError` instead of passing silently.

- A model instance's primary key now appears in the default `Model.__str__()` method, e.g. `Question object (1)`.

- `makemigrations` now detects changes to the model field `limit_choices_to` option. Add this to your existing migrations or accept an auto-generated migration for fields that use it.

- Performing queries that require automatic spatial transformations now raises `NotImplementedError` on MySQL instead of silently using non-transformed geometries.

- `django.core.exceptions.DjangoRuntimeWarning` is removed. It was only used in the cache backend as an intermediate class in `CacheKeyWarning`'s inheritance of `RuntimeWarning`.

- Renamed `BaseExpression._output_field` to `output_field`. You may need to update custom expressions.

- In older versions, forms and formsets combine their `Media` with widget `Media` by concatenating the two. The combining now tries to preserve the relative order of elements in each list. `MediaOrderConflictWarning` is issued if the order can't be preserved.

- `django.contrib.gis.gdal.OGRException` is removed. It's been an alias for `GDALException` since Django 1.8.

- Support for GEOS 3.3.x is dropped.

- The way data is selected for `GeometryField` is changed to improve performance, and in raw SQL queries, those fields must now be wrapped in `connection.ops.select`. See the Raw queries note in the GIS tutorial for an example.

## Features deprecated in 2.0

### `context` argument of `Field.from_db_value()` and `Expression.convert_value()`

The `context` argument of `Field.from_db_value()` and `Expression.convert_value()` is unused as it's always an empty dictionary. The signature of both methods is now:

    (self, value, expression, connection)

instead of:

    (self, value, expression, connection, context)

Support for the old signature in custom fields and expressions remains until Django 3.0.

### Miscellaneous

- The `django.db.backends.postgresql_psycopg2` module is deprecated in favor of `django.db.backends.postgresql`. It's been an alias since Django 1.9. This only affects code that imports from the module directly. The `DATABASES` setting can still use `'django.db.backends.postgresql_psycopg2'`, though you can simplify that by using the `'django.db.backends.postgresql'` name added in Django 1.9.
- `django.shortcuts.render_to_response()` is deprecated in favor of `django.shortcuts.render()`. `render()` takes the same arguments except that it also requires a `request`.
- The `DEFAULT_CONTENT_TYPE` setting is deprecated. It doesn't interact well with third-party apps and is obsolete since HTML5 has mostly superseded XHTML.
- `HttpRequest.xreadlines()` is deprecated in favor of iterating over the request.
- The `field_name` keyword argument to `QuerySet.earliest()` and `QuerySet.latest()` is deprecated in favor of passing the field names as arguments. Write `.earliest('pub_date')` instead of `.earliest(field_name='pub_date')`.

## Features removed in 2.0

These features have reached the end of their deprecation cycle and are removed in Django 2.0.

See Features deprecated in 1.9 for details on these changes, including how to remove usage of these features.

- The `weak` argument to `django.dispatch.signals.Signal.disconnect()` is removed.
- `django.db.backends.base.BaseDatabaseOperations.check_aggregate_support()` is removed.
- The `django.forms.extras` package is removed.
- The `assignment_tag` helper is removed.
- The `host` argument to `SimpleTestCase.assertsRedirects()` is removed. The compatibility layer which allows absolute URLs to be considered equal to relative ones when the path is identical is also removed.
- `Field.rel` and `Field.remote_field.to` are removed.
- The `on_delete` argument for `ForeignKey` and `OneToOneField` is now required in models and migrations. Consider squashing migrations so that you have fewer of them to update.
- `django.db.models.fields.add_lazy_relation()` is removed.
- When time zone support is enabled, database backends that don't support time zones no longer convert aware datetimes to naive values in UTC anymore when such values are passed as parameters to SQL queries executed outside of the ORM, e.g. with `cursor.execute()`.
- `django.contrib.auth.tests.utils.skipIfCustomUser()` is removed.
- The `GeoManager` and `GeoQuerySet` classes are removed.
- The `django.contrib.gis.geoip` module is removed.
- The `supports_recursion` check for template loaders is removed from:
  - `django.template.engine.Engine.find_template()`
  - `django.template.loader_tags.ExtendsNode.find_template()`
  - `django.template.loaders.base.Loader.supports_recursion()`
  - `django.template.loaders.cached.Loader.supports_recursion()`
- The `load_template` and `load_template_sources` template loader methods are removed.
- The `template_dirs` argument for template loaders is removed:
  - `django.template.loaders.base.Loader.get_template()`
  - `django.template.loaders.cached.Loader.cache_key()`
  - `django.template.loaders.cached.Loader.get_template()`
  - `django.template.loaders.cached.Loader.get_template_sources()`
  - `django.template.loaders.filesystem.Loader.get_template_sources()`
- `django.template.loaders.base.Loader.__call__()` is removed.
- Support for custom error views that don't accept an `exception` parameter is removed.
- The `mime_type` attribute of `django.utils.feedgenerator.Atom1Feed` and `django.utils.feedgenerator.RssFeed` is removed.
- The `app_name` argument to `include()` is removed.
- Support for passing a 3-tuple (including `admin.site.urls`) as the first argument to `include()` is removed.
- Support for setting a URL instance namespace without an application namespace is removed.
- `Field._get_val_from_obj()` is removed.
- `django.template.loaders.eggs.Loader` is removed.
- The `current_app` parameter to the `contrib.auth` function-based views is removed.
- The `callable_obj` keyword argument to `SimpleTestCase.assertRaisesMessage()` is removed.
- Support for the `allow_tags` attribute on `ModelAdmin` methods is removed.
- The `enclosure` keyword argument to `SyndicationFeed.add_item()` is removed.
- The `django.template.loader.LoaderOrigin` and `django.template.base.StringOrigin` aliases for `django.template.base.Origin` are removed.

See Features deprecated in 1.10 for details on these changes.

- The `makemigrations --exit` option is removed.
- Support for direct assignment to a reverse foreign key or many-to-many relation is removed.
- The `get_srid()` and `set_srid()` methods of `django.contrib.gis.geos.GEOSGeometry` are removed.
- The `get_x()`, `set_x()`, `get_y()`, `set_y()`, `get_z()`, and `set_z()` methods of `django.contrib.gis.geos.Point` are removed.
- The `get_coords()` and `set_coords()` methods of `django.contrib.gis.geos.Point` are removed.
- The `cascaded_union` property of `django.contrib.gis.geos.MultiPolygon` is removed.
- `django.utils.functional.allow_lazy()` is removed.
- The `shell --plain` option is removed.
- The `django.core.urlresolvers` module is removed in favor of its new location, `django.urls`.
- `CommaSeparatedIntegerField` is removed, except for support in historical migrations.
- The template `Context.has_key()` method is removed.
- Support for the `django.core.files.storage.Storage.accessed_time()`, `created_time()`, and `modified_time()` methods is removed.
- Support for query lookups using the model name when `Meta.default_related_name` is set is removed.
- The MySQL `__search` lookup is removed.
- The shim for supporting custom related manager classes without a `_apply_rel_filters()` method is removed.
- Using `User.is_authenticated()` and `User.is_anonymous()` as methods rather than properties is no longer supported.
- The `Model._meta.virtual_fields` attribute is removed.
- The keyword arguments `virtual_only` in `Field.contribute_to_class()` and `virtual` in `Model._meta.add_field()` are removed.
- The `javascript_catalog()` and `json_catalog()` views are removed.
- `django.contrib.gis.utils.precision_wkt()` is removed.
- In multi-table inheritance, implicit promotion of a `OneToOneField` to a `parent_link` is removed.
- Support for `Widget._format_value()` is removed.
- `FileField` methods `get_directory_name()` and `get_filename()` are removed.
- The `mark_for_escaping()` function and the classes it uses: `EscapeData`, `EscapeBytes`, `EscapeText`, `EscapeString`, and `EscapeUnicode` are removed.
- The `escape` filter now uses `django.utils.html.conditional_escape()`.
- `Manager.use_for_related_fields` is removed.
- Model `Manager` inheritance follows MRO inheritance rules. The requirement to use `Meta.manager_inheritance_from_future` to opt-in to the behavior is removed.
- Support for old-style middleware using `settings.MIDDLEWARE_CLASSES` is removed.