Changed %r to %s in get_language_info error message.
Merge pull request #791 from khalas/ticket_19811

Changed %r to %s in get_language_info error message
One last final fix for 0ad76843. Tested on py3 and py2
Fixed #19698 -- Cleared sites cache with signals

Thanks ddavies at nomensa.com for the report and the patch and
serdaroncode for reviewing the patch.
Added a draft document explaining how to release Django.

Thanks to James for the first draft; I made a few changes (svn->git) and
some supporting links, but mostly I added FIXME's.
Some updates to "how to release Django":

Typo fixes, spell check, some more specifics where possible.