Refs #16630.

fixed rfc comment typo in middleware/csrf.py

The problem description in #18239 asserted that
http://bugs.python.org/issue670664 was fixed in Python 2.6.8, but based on
http://bugs.python.org/issue670664#msg146770 it appears that's not correct; the
fix was only applied in 2.7, 3.2, and Python trunk. Therefore we must use our
patched HTMLParser subclass in all Python 2.6 versions.

The previously-referenced wiki page documents backwards-incompatible
changes from .96 to 1.0. Changed that referece to point to current
in-development release notes, which is where such changes are now
documented.

In an ideal world, nothing except django.db.models.query should have to
import stuff from django.models.sql.*. A few things were needing to get
hold of sql.constants.LOOKUP_SEP, so this commit moves it up to
django.db.models.constants.LOOKUP_SEP.

There are still a couple of places (admin) poking into sql.* to get
QUERY_TERMS, which is unfortunate, but a slightly different issue and
harder to adjust.

Thanks UloPe and Eric Florenzano for the patch, and Malcolm Tredinnick for
review.

Fixed #18545 -- Make the 'no DJANGO_SETTINGS_MODULE' error message more useful.Thanks Nick Coghlan for the report, and Malcolm Tredinnick for review.

Ticket 18657: Fix inconsistent DB names in router example.

This rewrites the entire example to use the same DB names throughout,
and also is hopefully a bit more sensibly described. Additionally, the
missing import of the random module for choosing a read slave is
included in the example now.

Some backends issue a warning here, others not. This is not the primary
goal of the test, so the assertion about the warning has been removed.
Thanks Carl Meyer for noticing the issue and suggesting the fix.

Fixed #18832 - Updated ModelForm example fields to match note below

Fixed a typo in the Python 3 compatibility docs.

Fixes #18245. Refs #3542.

Removed admin's swallowing of AttributeError (#16655, #18593, #18747)

During the new-admin changes, catching of AttributeError was added to
the admin.  This patch removes that as it's no longer possible to add a
value to a ModelAdmin that is not available.  Adding an attribute that
can not be called causes an ImproperlyConfigured exception to be raised.

Thanks mrmagooey for the draft patch.

Refs #16023.

Thanks Nick Martini for the patch.

Fixed #18928 - Tightened language in docs/README