Fixed syntax error in OSMWidget
Prevented rendering attrs to be squashed in OSMWidget
Fixed #21002 -- Documented JSON session serialization requires string keys

Thanks jeroen.pulles at redslider.net for the report.
Isolated map creation JS code
Fixed #21003 -- Ensured geometry widget return value has SRID

Thanks Mathieu Leplatre for the report and initial patch.
Fixed #20973 -- Document serving static files without django.contrib.staticfiles
Silenced deprecation warnings in SortedDict tests; refs [07876cf02b]
Removed references to django.utils.unittest which is PendingDeprecation
Silenced deprecation warning regarding old SQL location; refs #14300
Fixed #21026 -- Corrected help for manage.py test command.
Updated syncdb -> migrate in tests.
Fixed a couple unclosed file warnings in tests
Fixed "indentation is not a multiple of four" pep8 issues.
Clarified docs for some tags and filters
Fixed #20958 -- Documented that GenericForeignKey fields can't be accessed in forms.

Thanks marky1991.
Fixed #21010 -- Changed ModelState to only copy _meta.local_fields.
Removed "makemigrations --force" from docs since it doesn't actually exist.
Updated six to version 1.4.1.
Tested exc_type instead of exc_value in __exit__.

exc_value might be None even though there's an exception, at least on
Python 2.6. Thanks Thomas Chaumeny for the report.

Fixed #21034.

Forward-port of a8624b2 from 1.6.x.
Fixed #21009 -- Added a versionchanged note regarding changes to clean().

refs [fb1dd6b13a] and [1c4a9bd9ad1]