Merged revisions 81380 via svnmerge from

Merged revisions 81380 via svnmerge from
svn+ssh://pythondev@svn.python.org/python/trunk

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  r81380 | brett.cannon | 2010-05-20 11:37:55 -0700 (Thu, 20 May 2010) | 8 lines

  Turned out that if you used explicit relative import syntax
  (e.g. from .os import sep) and it failed, import would still try the implicit
  relative import semantics of an absolute import (from os import sep). That's
  not right, so when level is negative, only do explicit relative import
  semantics.

  Fixes issue #7902. Thanks to Meador Inge for the patch.
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