Undelete the login() call inadvertantly removed in 4e0a2fe59c

Refs #21271.
Fixed typo in docs/releases/1.4.9.txt.
Fixed #21325 -- Added missing argument to permission_required decorator.
Fixed up some more flake8 violations (this particular violation still has many occurrences in the tests/ dir so it can't be removed from setup.cfg yet)
Fix all violators of E231
Fixed #21335 -- Use importlib from python3 when using python3
Fixed all the E203 violations
Remove dsome import *
Fix note syntax usage.

http://sphinx.readthedocs.org/en/latest/markup/para.html?highlight=note#directive-note
Merge pull request #1818 from ericholscher/small-doc-fix

Fix note syntax usage.
Fixed test that reads a migration file from disk.

We need to make sure content read from the file is decoded from UTF-8
right from the start so Python doesn't try to use another encoding
(read: ASCII/CP1252 under Windows.)
Rearranged some file-related tests

Just moving around some tests to be more logically grouped.
Rearranged some i18n tests

Compilation/extraction tests are now properly skipped when gettext
commands are unavailable.
Fixed #21344 -- Typo in docs/ref/models/queries.txt
Mark this as a python code-block
Use `callable` instead of `six.callable`.

The `callable` builtin was added back in python 3.2
which is the minimal python3 version supported by django
at this point.
Fixed #8261 -- ModelAdmin hook for customising the "show on site" button

``ModelAdmin.view_on_site`` defines wether to show a link to the object on the
admin detail page. If ``True``, cleverness (i.e. ``Model.get_absolute_url``) is
used to get the url. If it's a callable, the callable is called with the object
as the only parameter. If ``False``, not link is displayed.

With the aim of maitaining backwards compatibility, ``True`` is the default.
Fixed a F811 warning introduced by 35db9d58d6.
Fixed #21345: Don't evaluate callable settings in the debug page.

Thanks to crass for the report.
Added some more tests for the debug page.

* Missing tests for ticket #12744
* Tests for the cleanse_setting feature (leaving out sensitive
  settings from the debug page)