# Documentazione Django 6.0.7

# Note di rilascio di Django 1.11

4 Aprile 2017

Welcome to Django 1.11!

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 1.10 or older versions. We’ve begun the deprecation process for some features.

See the Come aggiornare Django ad una nuova versione guide if you’re updating an existing project.

Django 1.11 is designated as a 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.

## Compatibilità con Python

Django 1.11 requires Python 2.7, 3.4, 3.5, 3.6, or 3.7 (as of 1.11.17). 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 3.4+.

## 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.

## What’s new in Django 1.11

### Class-based model indexes

The new `django.db.models.indexes` module contains classes which ease creating database indexes. Indexes are added to models using the `Meta.indexes` option.

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

### Template-based widget rendering

To ease customizing widgets, form widget rendering is now done using the template system rather than in Python. See The form rendering API.

You may need to adjust any custom widgets that you’ve written for a few backwards incompatible changes.

### `Subquery` expressions

The new `Subquery` and `Exists` database expressions allow creating explicit subqueries. Subqueries may refer to fields from the outer queryset using the `OuterRef` class.

### Minor features

#### `django.contrib.admin`

- `ModelAdmin.date_hierarchy` can now reference fields across relations.

- The new `ModelAdmin.get_exclude()` hook allows specifying the exclude fields based on the request or model instance.

- The `popup_response.html` template can now be overridden per app, per model, or by setting the `ModelAdmin.popup_response_template` attribute.

#### `django.contrib.auth`

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

- The `LoginView` and `LogoutView` class-based views supersede the deprecated `login()` and `logout()` function-based views.

- The `PasswordChangeView`, `PasswordChangeDoneView`, `PasswordResetView`, `PasswordResetDoneView`, `PasswordResetConfirmView`, and `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 `PasswordResetConfirmView` allows automatically logging in a user after a successful password reset. If you have multiple `AUTHENTICATION_BACKENDS` configured, use the `post_reset_login_backend` attribute to choose which one to use.

- To avoid the possibility of leaking a password reset token via the HTTP Referer header (for example, if the reset page includes a reference to CSS or JavaScript hosted on another domain), the `PasswordResetConfirmView` (but not the deprecated `password_reset_confirm()` function-based view) stores the token in a session and redirects to itself to present the password change form to the user without the token in the URL.

- `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 `LoginView` and `LogoutView` allows specifying a set of hosts that are safe for redirecting after login and logout.

- Added password validators `help_text` to `UserCreationForm`.

- The `HttpRequest` is now passed to `authenticate()` which in turn passes it to the authentication backend if it accepts a `request` argument.

- The `user_login_failed()` signal now receives a `request` argument.

- `PasswordResetForm` supports custom user models that use an email field named something other than `'email'`. Set `CustomUser.EMAIL_FIELD` to the name of the field.

- `get_user_model()` can now be called at import time, even in modules that define models.

#### `django.contrib.contenttypes`

- When stale content types are detected in the `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).

#### `django.contrib.gis`

- The new `GEOSGeometry.from_gml()` and `OGRGeometry.from_gml()` methods allow creating geometries from GML.

- Added support for the `dwithin` lookup on SpatiaLite.

- The `Area` function, `Distance` function, and distance lookups now work with geodetic coordinates 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 old `https://openlayers.org/` source. They are also updated to use OpenLayers 3.

- PostGIS migrations can now change field dimensions.

- Added the ability to pass the `size`, `shape`, and `offset` parameters when creating `GDALRaster` objects.

- Added SpatiaLite support for the `IsValid` function, `MakeValid` function, and `isvalid` lookup.

- Added Oracle support for the `AsGML` function, `BoundingCircle` function, `IsValid` function, and `isvalid` lookup.

#### `django.contrib.postgres`

- The new `distinct` argument for `StringAgg` determines if concatenated values will be distinct.

- The new `GinIndex` and `BrinIndex` classes allow creating `GIN` and `BRIN` indexes in the database.

- `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 `CIText` mixin and `CITextExtension` migration operation allow using PostgreSQL’s `citext` extension for case-insensitive lookups. Three fields are provided: `CICharField`, `CIEmailField`, and `CITextField`.

- The new `JSONBAgg` allows aggregating values as a JSON array.

- The `HStoreField` (model field) and `HStoreField` (form field) allow storing null values.

#### Cache

- Memcached backends now pass the contents of `OPTIONS` as keyword arguments to the client constructors, allowing for more advanced control of client behavior. See the cache arguments documentation for examples.

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

#### CSRF

- Added the `CSRF_USE_SESSIONS` setting to allow storing the CSRF token in the user’s session rather than in a cookie.

#### Database backends

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

- Added the `TEST['TEMPLATE']` setting to let PostgreSQL users specify a template for creating the test database.

- `QuerySet.iterator()` now uses server-side cursors on PostgreSQL. This feature transfers some of the worker memory load (used to hold query results) to the database and might increase database memory usage.

- Added MySQL support for the `'isolation_level'` option in `OPTIONS` to allow specifying the transaction isolation level. To avoid possible data loss, it’s recommended to switch from MySQL’s default level, repeatable read, to read committed.

- Added support for `cx_Oracle` 5.3.

#### Email

- Added the `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 `io.TextIOWrapper`, `File` now has the `readable()`, `writable()`, and `seekable()` methods.

#### I Form

- The new `empty_value` attribute on `CharField`, `EmailField`, `RegexField`, `SlugField`, and `URLField` allows specifying the Python value to use to represent «empty».

- The new `Form.get_initial_for_field()` method returns initial data for a form field.

#### Internationalization

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

#### Management Commands

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

- The new `diffsettings --default` option allows specifying a settings module other than Django’s default settings to compare against.

- `app_label`s arguments now limit the `showmigrations --plan` output.

#### Migrations

- Added support for serialization of `uuid.UUID` objects.

#### Modelli

- Added support for callable values in the `defaults` argument of `QuerySet.update_or_create()` and `get_or_create()`.

- `ImageField` now has a default `validate_image_file_extension` validator. (This validator moved to the form field in Django 1.11.2.)

- Added support for time truncation to `Trunc` functions.

- Added the `ExtractWeek` function to extract the week from `DateField` and `DateTimeField` and exposed it through the `week` lookup.

- Added the `TruncTime` function to truncate `DateTimeField` to its time component and exposed it through the `time` lookup.

- Added support for expressions in `QuerySet.values()` and `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 `FileField`.

- Added the `nulls_first` and `nulls_last` parameters to `Expression.asc()` and `desc()` to control the ordering of null values.

- The new `F` expression `bitleftshift()` and `bitrightshift()` methods allow bitwise shift operations.

- Added `QuerySet.union()`, `intersection()`, and `difference()`.

#### Requests and Responses

- Added `QueryDict.fromkeys()`.

- `CommonMiddleware` now sets the `Content-Length` response header for non-streaming responses.

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

- `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 JSON serializer can now be customized by passing a `cls` keyword argument to the `serializers.serialize()` function.

- `DjangoJSONEncoder` now serializes `timedelta` objects (used by `DurationField`).

#### Template

- `mark_safe()` can now be used as a decorator.

- The `Jinja2` template backend now supports context processors by setting the `'context_processors'` option in `OPTIONS`.

- The `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 `resetcycle` template tag to allow resetting the sequence of the `cycle` template tag.

- You can now specify specific directories for a particular `filesystem.Loader`.

#### Tests

- Added `DiscoverRunner.get_test_runner_kwargs()` to allow customizing the keyword arguments passed to the test runner.

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

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

- Added support for `unittest.TestCase.subTest()`’s when using the `test --parallel` option.

- `DiscoverRunner` now runs the system checks at the start of a test run. Override the `DiscoverRunner.run_checks()` method if you want to disable that.

#### Validators

- Added `FileExtensionValidator` to validate file extensions and `validate_image_file_extension` to validate image files.

## Backwards incompatible changes in 1.11

### `django.contrib.gis`

- To simplify the codebase and because it’s easier to install than when `contrib.gis` was first released, GDAL 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.

- The `GEOSGeometry` equality operator now also compares SRID.

- The OpenLayers-based form widgets now use OpenLayers 3, and the `gis/openlayers.html` and `gis/openlayers-osm.html` templates have been updated. Check your project if you subclass these widgets or extend the templates. Also, the new widgets work a bit differently than the old ones. Instead of using a toolbar in the widget, you click to draw, click and drag to move the map, and click and drag a point/vertex/corner to move it.

- Support for SpatiaLite < 4.0 is dropped.

- Support for GDAL 1.7 and 1.8 is dropped.

- The widgets in `contrib.gis.forms.widgets` and the admin’s `OpenLayersWidget` use the form rendering API rather than `loader.render_to_string()`. If you’re using a custom widget template, you’ll need to be sure your form renderer can locate it. For example, you could use the `TemplatesSetting` renderer.

### `django.contrib.staticfiles`

- `collectstatic` may now fail during post-processing when using a hashed static files storage if a reference loop exists (e.g. `'foo.css'` references `'bar.css'` which itself references `'foo.css'`) or if the chain of files referencing other files is too deep to resolve in several passes. In the latter case, increase the number of passes using `ManifestStaticFilesStorage.max_post_process_passes`.

- When using `ManifestStaticFilesStorage`, static files not found in the manifest at runtime now raise a `ValueError` instead of returning an unchanged path. You can revert to the old behavior by setting `ManifestStaticFilesStorage.manifest_strict` to `False`.

### Database backend API

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

- 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 `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 ordering of each column in the index.

- `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()`.

- Renamed the `ignores_quoted_identifier_case` feature to `ignores_table_name_case` to more accurately reflect how it is used.

- The `name` keyword argument is added to the `DatabaseWrapper.create_cursor(self, name=None)` method to allow usage of server-side cursors on backends that support it.

### 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.

Also, the minimum supported version of psycopg2 is increased from 2.4.5 to 2.5.4.

### `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.

If you need to bind `LiveServerTestCase` to a specific port, use the `port` attribute added in Django 1.11.2.

### Protection against insecure redirects in `django.contrib.auth` and `i18n` views

`LoginView`, `LogoutView` (and the deprecated function-based equivalents), and `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, `get_or_create()` and `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:

    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 if there’s a use case where you find you can’t adapt your code to set a `TIME_ZONE`.

### HTML changes in admin templates

`<p class="help">` is replaced with a `<div>` tag to allow including lists inside help text.

Read-only fields are wrapped in `<div class="readonly">...</div>` instead of `<p>...</p>` to allow any kind of HTML as the field’s content.

### Changes due to the introduction of template-based widget rendering

Some undocumented classes in `django.forms.widgets` are removed:

- `SubWidget`

- `RendererMixin`, `ChoiceFieldRenderer`, `RadioFieldRenderer`, `CheckboxFieldRenderer`

- `ChoiceInput`, `RadioChoiceInput`, `CheckboxChoiceInput`

The undocumented `Select.render_option()` method is removed.

The `Widget.format_output()` method is removed. Use a custom widget template instead.

Some widget values, such as `<select>` options, are now localized if `settings.USE_L10N=True`. You could revert to the old behavior with custom widget templates that uses the `localize` template tag to turn off localization.

### `django.template.backends.django.Template.render()` prohibits non-dict context

For compatibility with multiple template engines, `django.template.backends.django.Template.render()` (returned from high-level template loader APIs such as `loader.get_template()`) must receive a dictionary of context rather than `Context` or `RequestContext`. If you were passing either of the two classes, pass a dictionary instead – doing so is backwards-compatible with older versions of Django.

### Model state changes in migration operations

To improve the speed of applying migrations, rendering of related models is delayed until an operation that needs them (e.g. `RunPython`). If you have a custom operation that works with model classes or model instances from the `from_state` argument in `database_forwards()` or `database_backwards()`, you must render model states using the `clear_delayed_apps_cache()` method as described in writing your own migration operation.

### Server-side cursors on PostgreSQL

The change to make `QuerySet.iterator()` use server-side cursors on PostgreSQL prevents running Django with PgBouncer in transaction pooling mode. To reallow that, use the `DISABLE_SERVER_SIDE_CURSORS` setting (added in Django 1.11.1) in `DATABASES`.

See Transaction pooling and server-side cursors for more discussion.

### Miscellanea

- If no items in the feed have a `pubdate` or `updateddate` attribute, `SyndicationFeed.latest_post_date()` now returns the current UTC date/time, instead of a datetime without any timezone information.

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

- `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 `ALLOWED_HOSTS`. See Tests and multiple host names.

- 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, `CharField` with `null=True` now saves `NULL` for blank values instead of empty strings.

- On Oracle, `Model.validate_unique()` no longer checks empty strings for uniqueness as the database interprets the value as `NULL`.

- If you subclass `AbstractUser` and override `clean()`, be sure it calls `super()`. `BaseUserManager.normalize_email()` is called in a new `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 always 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'`.

- `RelatedManager.add()`, `remove()`, `clear()`, and `set()` now clear the `prefetch_related()` cache.

- To prevent possible loss of saved settings, `setup_test_environment()` now raises an exception if called a second time before calling `teardown_test_environment()`.

- The undocumented `DateTimeAwareJSONEncoder` alias for `DjangoJSONEncoder` (renamed in Django 1.0) is removed.

- The `cached template loader` is now enabled if `OPTIONS['loaders']` isn’t specified and `OPTIONS['debug']` is `False` (the latter option defaults to the value of `DEBUG`). This could be backwards-incompatible if you have some template tags that aren’t thread safe.

- The prompt for stale content type deletion no longer occurs after running the `migrate` command. Use the new `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.

- `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`. `UpdateCacheMiddleware` and `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. It also no longer sets the `Content-Length` header as this is now done by `CommonMiddleware`.

  If you have a middleware that modifies a response’s content and appears before `CommonMiddleware` in the `MIDDLEWARE` or `MIDDLEWARE_CLASSES` settings, you must reorder your middleware so that responses aren’t modified after `Content-Length` is set, or have the response modifying middleware reset the `Content-Length` header.

- `get_model()` and `get_models()` now raise `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`.

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

- The undocumented `django.utils.functional.lazy_property` is removed.

- For consistency with non-multipart requests, `MultiPartParser.parse()` now leaves `request.POST` immutable. If you’re modifying that `QueryDict`, you must now first copy it, e.g. `request.POST.copy()`.

- Support for `cx_Oracle` < 5.2 is removed.

- Support for IPython < 1.0 is removed from the `shell` command.

- The signature of private API `Widget.build_attrs()` changed from `extra_attrs=None, **kwargs` to `base_attrs, extra_attrs=None`.

- File-like objects (e.g., `StringIO` and `BytesIO`) uploaded to an `ImageField` using the test client now require a `name` attribute with a value that passes the `validate_image_file_extension` validator. See the note in `Client.post()`.

- `FileField` now moves rather than copies the file it receives. With the default file upload settings, files larger than `FILE_UPLOAD_MAX_MEMORY_SIZE` now have the same permissions as temporary files (often `0o600`) rather than the system’s standard umask (often `0o6644`). Set the `FILE_UPLOAD_PERMISSIONS` if you need the same permission regardless of file size.

## Features deprecated in 1.11

### `models.permalink()` decorator

Use `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])

### Miscellanea

- `contrib.auth`’s `login()` and `logout()` function-based views are deprecated in favor of new class-based views `LoginView` and `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 `PasswordChangeView`, `PasswordChangeDoneView`, `PasswordResetView`, `PasswordResetDoneView`, `PasswordResetConfirmView`, and `PasswordResetCompleteView`.

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

- `django.utils.translation.string_concat()` is deprecated in favor of `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 `{% 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()`.

- `authenticate()` now passes a `request` argument to the `authenticate()` method of authentication backends. Support for methods that don’t accept `request` as the first positional argument will be removed in Django 2.1.

- The `USE_ETAGS` setting is deprecated in favor of `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.

- `Model._meta.has_auto_field` is deprecated in favor of checking if `Model._meta.auto_field is not None`.

- Using regular expression groups with `iLmsu#` in `url()` is deprecated. The only group that’s useful is `(?i)` for case-insensitive URLs, however, case-insensitive URLs aren’t a good practice because they create multiple entries for search engines, for example. An alternative solution could be to create a `handler404` that looks for uppercase characters in the URL and redirects to a lowercase equivalent.

- The `renderer` argument is added to the `Widget.render()` method. Methods that don’t accept that argument will work through a deprecation period.