Merged revisions 78412 via svnmerge from

Merged revisions 78412 via svnmerge from
svn+ssh://pythondev@svn.python.org/python/trunk

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  r78412 | r.david.murray | 2010-02-23 21:31:27 -0500 (Tue, 23 Feb 2010) | 6 lines

  Issue 7975: in python 2.6 bsddb.dbshelve switched from DictMixin to
  MutableMapping, and thereby lost functionality because the replacement
  functionality was implemented incorrectly or incompletely).  Since bsddb
  isn't in py3k, this patch just goes back to using DictMixin in order to
  correct the regression.
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