This allows dynamically-generated attributes to be specified in
checked ModelAdmin attributes without triggering errors.

Düsseldorf now appears as Dusseldorf in the latest version
of the GeoIP2 database.

Django 1.9 drops support for PostgreSQL 9.0 where creating
a database using a template was needed.

Sigh.

This was the original intent.

textwrap.indent() is new in Python 3.3.

Fixed #20461 -- Allowed running tests in parallel.

This reduces the time spent cloning databases.

Thanks Tim for the suggestion.

Subclass private APIs is marginally better than monkey-patching them,
even if it doesn't make a big difference in practice.

This new technique is more straightforward and compatible with test
parallelization, where the effective database connection settings no
longer match settings.DATABASES.

Notably it will fail to report a Model.DoesNotExist exceptions because
the class itself isn't pickleable. (Django has specific code to make its
instances pickleable.)

Considering the APIs exercised by these test cases, it's hard to make
them independent.

This requires that each test never alters files in static directories
collected by other tests. The alternative is to add a temporary
directory to STATICFILES_DIRS or a new app to INSTALLED_APPS.

This is required for running tests in parallel.

The previous implementation would result in tests hitting the wrong
database when running tests in parallel on multiple databases.

Previously, a traceback would be displayed on exit because:
- using some multiprocessing features creates a temporary directory
- this directory would be inside TMPDIR
- multiprocessing would attempt to remove it when a particular object
  was deallocated, after runtests.py had already removed it along with
  everything else in TMPDIR.

This prevented the temporary directory from being removed
on Windows.

Thanks Jaap Roes for the idea and initial patch.