Recorded merge of revisions 75123 via svnmerge from

svn+ssh://pythondev@svn.python.org/python/trunk

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  r75123 | philip.jenvey | 2009-09-28 21:32:44 -0700 (Mon, 28 Sep 2009) | 4 lines

  #6990: clear threading.local's key only after its thread state is removed:
  fixes local subclasses leaving old state around after a ref cycle GC which
  could be recycled by new locals
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