[docs] [issue12644] document the "%a" conversion in the old string formatting operations

[Ezio Melotti]

Ezio Melotti <ezio.melotti at gmail.com> added the comment:

The commit looks fine, the issue can be closed.

----------

_______________________________________
Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue12644>
_______________________________________