Merged revisions 77157 via svnmerge from

Merged revisions 77157 via svnmerge from
svn+ssh://pythondev@svn.python.org/python/trunk

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  r77157 | benjamin.peterson | 2009-12-30 13:34:10 -0600 (Wed, 30 Dec 2009) | 5 lines

  check if the attribute is set before deleting it with T_OBJECT_EX (fixes #7604)

  Also, add a note to the docs about the better behavior of T_OBJECT_EX as
  compared to T_OBJECT.
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