the io module was added in 2.6 (I know not really, but the end user isn't...

the io module was added in 2.6 (I know not really, but the end user isn't going to care about backporting.)

Doc/library/io.rst

@@ -7,6 +7,7 @@
 .. moduleauthor:: Mike Verdone <mike.verdone@gmail.com>
 .. moduleauthor:: Mark Russell <mark.russell@zen.co.uk>
 .. sectionauthor:: Benjamin Peterson
+.. versionadded:: 2.6
 
 The :mod:`io` module provides the Python interfaces to stream handling.  The
 builtin :func:`open` function is defined in this module.