[issue2877] Backport UserString move from 3.0

[Brett Cannon]

New submission from Brett Cannon <brett at python.org>:

The UserString class was moved from its own module to the collections 
module. That change needs to be backported.

----------
components: Library (Lib)
messages: 66901
nosy: brett.cannon
priority: release blocker
severity: normal
status: open
title: Backport UserString move from 3.0
type: behavior
versions: Python 2.6

__________________________________
Tracker <report at bugs.python.org>
<http://bugs.python.org/issue2877>
__________________________________