Refs #13573 -- Modified the key technique added in r13295 to be more robust...

Refs #13573 -- Modified the key technique added in r13295 to be more robust against potential key collisions while keeping key names human-readable. Thanks to Alex for being finicky.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@13299 bcc190cf-cafb-0310-a4f2-bffc1f526a37