Fixed #21856: Allow Empty DATABASES Setting

Used available_attrs in method_decorator

There wasn't any file locking under Windows unless PyWin32 was
installed. This removes that (undocumented) dependency by using ctypes
instead.

Thanks to Anatoly Techtonik for writing the ctypes port upon which this
is based.

Thanks rmoe for the report and the patch.

Thanks Aymeric Augustin for the suggestion and review.

Remove check_migrations from the runserver command and use the new checks framework to check for unapplied migrations. Don't check for migrations if the DATABASES setting is empty.

Adds Australian English (en_AU) to locale conf, which differs from
American English in date formatting and spelling, and continues
to diverge from British English in spelling (and first-day-of-week
according to the current en_GB locale format.py).

The transifex language project to match this patch has been requested.

Thanks Zach Smith for the patch.

Thanks keturn for the reporti, Chris Medrela for details and
Tim Graham for the review.
Refs #19915.

Overriding the error messages now works for both unique fields, unique_together
and unique_for_date.

This patch changed the overriding logic to allow customizing NON_FIELD_ERRORS
since previously only fields' errors were customizable.

Refs #20199.

Thanks leahculver for the suggestion.

Thanks Aymeric Augustin and Simon Charette for reviews.

MySQL does allow primary key with value 0. It only forbids autoincrement
primary key with value 0.

Thanks Claude Paroz for the report.

Thanks jordan at aace.org for the suggestion.

Refs #20625.

This reverts commit 2ee447fb.

That commit introduced a regression (#21882) and didn't really
do what it was supposed to: while it did delay the evaluation
of lazy objects passed to mark_safe(), they weren't actually
marked as such so they could end up being escaped twice.

Refs #21882.

Refs #21952

Thanks Michael Manfre for the report.

Refs #21911. Now that we have a more traditional login form, we
don't need any more a special field telling us we are dealing with
the login form.

Historically, the Django admin used to pass through the request
from an unauthorized access to the login view directly. Now we
are using a proper redirection, which is also preventing
inadvertantly changing data when POSTing login data to an admin
view when user is already authorized.
Thanks Marc Tamlyn and Tim Graham for the reviews.

Refs #21911.

Made sure Django treats case .filter(NOT (a AND b)) the same way as
.filter((NOT a OR NOT b)) for join promotion.

Thanks Siecje.