[issue12907] Update test coverage devguide page

Changes by Dougal Matthews douga...@gmail.com: -- nosy: +d0ugal ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue12907 ___ ___ Python-bugs-list

[issue13498] os.makedirs exist_ok documentation is incorrect, as is some of the behavior

Changes by Dougal Matthews douga...@gmail.com: -- nosy: +d0ugal ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue13498 ___ ___ Python-bugs-list