Blocked revisions 63767 via svnmerge

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  r63767 | brett.cannon | 2008-05-28 22:08:50 -0700 (Wed, 28 May 2008) | 4 lines

  UserString.MutableString has been removed in Python 3.0.

  Works on issue #2877. Thanks Quentin Gallet-Gilles for the patch.
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