Removed a bunch of Python 2.4 workarounds now that we don't support it. Refs...

Removed a bunch of Python 2.4 workarounds now that we don't support it. Refs #15702 -- thanks to jonash for the patch. Splitting this over muliple commits to make it more manageable.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@15926 bcc190cf-cafb-0310-a4f2-bffc1f526a37