Refs #19571

Thanks rodrigorosa.lg and others for the report.

The original problem was that queryset cloning was really expensive
when filtering with F() clauses. The __deepcopy__ went too deep copying
_meta attributes of the models used. To fix this the use of
__deepcopy__ in qs cloning was removed.

This commit results in some speed improvements across the djangobench
benchmark suite. Most query_* tests are 20-30% faster, save() is 50%
faster and finally complex filtering situations can see 2x to order
of magnitude improvments.

Thanks to Suor, Alex and lrekucki for valuable feedback.

Refs #19441.

The tickets are either about different signature between qs.none() and
qs or problems with subclass types (either EmptyQS overrided the custom
qs class, or EmptyQS was overridden by another class - values() did
this).

Fixed #15959, fixed #17271, fixed #17712, fixed #19426

The guarantee that no queries will be made when accessing results is
done by new EmptyWhere class which is used for query.where and having.

Thanks to Simon Charette for reviewing and valuable suggestions.

Thanks Beuc for the report and the initial patch.

Thanks Simon Charette for the initial patch, and Jan Bednařík for
his work on the ticket.

The exact conditions on which this exception is raised are not
known, but this replacement is the best guess we can do at this
point.

Thanks Sebastian Noack for the report and the initial patch.

Thanks Sebastian Noack for the report and the initial patch.

PostGIS 2.0.2 has been released on December 3rd 2012, with the
fix included.

Added -n to sphinx builds to catch issues going forward.

Slightly reworded another related paragraph for clarity, too.

* Fixed JSON indentation.
* Avoided relying on implicit ordering.

When &'ing or |'ing querysets, wrong values could be cached, and crashes
could happen.

Thanks Marc Tamlyn for figuring out the problem and writing the patch.

Thanks jnns for the report.

* Used override_settings consistently -- changes to DEBUG could leak.
* Took advantage of assertRaisesRegexp.
* Fixed indentation -- some code was indented at 2 spaces.

Tiny typo fixed in logging docs

This includes fixes for the java/jython detection and a new license header.

Thanks to Thomas Bartelmess for the report.

Correct Lithuanian short date format.

Thx to Bouke Haarsma for the report.

This was caused by PIL raising a zlib truncated stream error since we fed
the parser with chunks instead of the whole image.

This allows for a behavior more in line with what is expected by Ipython
users, e.g. the user namespace is initialized from config files, startup
files.

Thanks Benjamin Ragan-Kelley from the IPython dev team for the patch.