Also renamed app_cache to apps and "app cache" to "app registry".

Deprecated AppCache.app_cache_ready() in favor of Apps.ready().

Reverted 4a56a93c.

Improved Andrew's hack to create temporary app caches to handle
migrations. Now the main app cache has a "master" flag set to True
(which is a non-default keyword argument, thus unlikely to be used by
mistake). Other app cache instances have "master" set to False.

The only sanctioned way to access the app cache is by importing
django.core.apps.app_cache.

If you were instanciating an app cache and relying on the Borg pattern,
you'll have to refactor your code.

This commit doesn't contain any code changes; it's purely a refactoring.

Thanks to Tim for the review.

Signed-off-by: Jason Myers <jason@jasonamyers.com>

* Removed trailing whitespace.
* Added newline to EOF if missing.
* Removed blank lines at EOF.
* Removed some stray tabs.

Should be unneeded with Python 2.7 and up.
Added some unicode_literals along the way.

Refs #20680.

Thanks Vinay Sajip for the support of his django3 branch and
Jannis Leidel for the review.

Thanks Clueless for the initial patch.
Note that unittest has been purposely left out (external package only used by Python 2.6).

git-svn-id: http://code.djangoproject.com/svn/django/trunk@17828 bcc190cf-cafb-0310-a4f2-bffc1f526a37

git-svn-id: http://code.djangoproject.com/svn/django/trunk@16986 bcc190cf-cafb-0310-a4f2-bffc1f526a37

git-svn-id: http://code.djangoproject.com/svn/django/trunk@16975 bcc190cf-cafb-0310-a4f2-bffc1f526a37

Fixed #16225 -- Removed unused imports. Many thanks to Aymeric Augustin for the work on the patch and Alex for reviewing.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@16539 bcc190cf-cafb-0310-a4f2-bffc1f526a37

Renamed a test model field added in [16345] so it doesn't keep the test DB ceation process from finishing under Oracle.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@16499 bcc190cf-cafb-0310-a4f2-bffc1f526a37

git-svn-id: http://code.djangoproject.com/svn/django/trunk@16357 bcc190cf-cafb-0310-a4f2-bffc1f526a37

git-svn-id: http://code.djangoproject.com/svn/django/trunk@16348 bcc190cf-cafb-0310-a4f2-bffc1f526a37

git-svn-id: http://code.djangoproject.com/svn/django/trunk@16345 bcc190cf-cafb-0310-a4f2-bffc1f526a37

Fixed #14951 -- Made the unique_for_{date,month,year} model field constraints to not fail when the related DateField is empty.

Existing modelforms tests were extended to cover this case and an equivalent set of tests was added for the model functionality.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@15167 bcc190cf-cafb-0310-a4f2-bffc1f526a37

Fixed #5416 -- Added TestCase.assertNumQueries, which tests that a given function executes the correct number of queries.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@14183 bcc190cf-cafb-0310-a4f2-bffc1f526a37

Fixed #12991 -- Added unittest2 support. Thanks to PaulM for the draft patch, and to Luke, Karen, Justin, Alex, Łukasz Rekucki, and Chuck Harmston for their help testing and reviewing the final patch.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@14139 bcc190cf-cafb-0310-a4f2-bffc1f526a37

Fixed #14102 -- Ensure that fields that have been excluded from a form aren't included in the unique_for_* checks, either. Thanks to Travis Cline for the report and fix.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@13598 bcc190cf-cafb-0310-a4f2-bffc1f526a37

git-svn-id: http://code.djangoproject.com/svn/django/trunk@12797 bcc190cf-cafb-0310-a4f2-bffc1f526a37

Fixed #12647. Allow unique_together checks be specified as lists as well as tuples. Thanks, Honza Král.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@12403 bcc190cf-cafb-0310-a4f2-bffc1f526a37

git-svn-id: http://code.djangoproject.com/svn/django/trunk@12227 bcc190cf-cafb-0310-a4f2-bffc1f526a37

Fixed #12512. Changed ModelForm to stop performing model validation on fields that are not part of the form. Thanks, Honza Kral and Ivan Sagalaev.
This reverts some admin and test changes from [12098] and also fixes #12507, #12520, #12552 and #12553.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@12206 bcc190cf-cafb-0310-a4f2-bffc1f526a37

git-svn-id: http://code.djangoproject.com/svn/django/trunk@12098 bcc190cf-cafb-0310-a4f2-bffc1f526a37