Our WSGIServer rewrapped the socket errors from server_bind into
WSGIServerExceptions, which is used later on to provide nicer
error messages in runserver and used by the liveserver to see if
the port is already in use. But wrapping server_bind isn't enough since
it only binds to the socket, socket.listen (which is called from
server_activate) could also raise "Address already in use".

Instead of overriding server_activate too I chose to just catch socket
errors, which seems to make more sense anyways and should be more robust
against changes in wsgiref.

Refs #20693.

Fixed #21141 -- Updated Sphinx URL.

Updated Sphinx URL from http://sphinx.pocoo.org/ to http://sphinx-doc.org/.

We have always been at war with trailing backslashes.

That commit didn't always improve readability.

See discussion on django-developers for details.

Fields must render values in the current time zone.

This commit only contains tests because this ticket was just a symptom of
a regression from #18777 that was fixed separately.

This is a follow-up to #18777 which improperly converted to strings in
prepare_value and as such caused regressions like #21074.

Refs #18777, #21074

Correct very minor typo

Just changed as to has.

Refs #19371.

Addressed inaccuracies in performance docs

* Move the discussion of CachedStaticFilesStorage to the section about
  HTTP. It's really about client-side caching. It doesn't fit with the
  caching utilities from django.utils.functional.

* Tone down the warning against Pypy as per Alex' feedback. It's a valid
  choice for advanced users who are comfortable using a non-standard
  stack.

* Generally reworded the 'Using different versions of available software'
  section.

* Some other minor adjustments to the document.

- missing __init__.py

Many thanks to all involved in discussions, and in particular to Tim Graham for painstaking reviews.

Thanks stanislas.guerra at gmail.com for the report.

Increase default PBKDF2 iterations

Thanks gsf for the suggestion.

Increases the default PBKDF2 iterations, since computers have gotten
faster since 2011. In the future, we plan to increment by 10% per
major version.

- Noted that this does not allow for reading and writing the same open
file in different processes under Windows.
- Noted that the keyword arguments to NamedTemporaryFile no longer
match the Python version.

Thanks tobias for the suggestion and boblefrag and saz for work on the
patch.

Thanks Alexey Boriskin for the report.

Fix #21121: Add archive of security issues.

Thanks stavros for the suggestion.