Blocked revisions 72172 via svnmerge

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  r72172 | walter.doerwald | 2009-05-01 21:58:58 +0200 (Fr, 01 Mai 2009) | 12 lines

  Merged revisions 72167 via svnmerge from
  svn+ssh://pythondev@svn.python.org/python/trunk

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    r72167 | walter.doerwald | 2009-05-01 19:35:37 +0200 (Fr, 01 Mai 2009) | 5 lines

    Make test.test_support.EnvironmentVarGuard behave like a dictionary.

    All changes are mirrored to the underlying os.environ dict, but rolled back
    on exit from the with block.
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