When stdout or stderr (but not both) are redirected and PYTHONIOENCODING is not set, test_sys is failed in 2.7.

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FAIL: test_43581 (test.test_sys.SysModuleTest)
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Traceback (most recent call last):
  File "/home/serhiy/py/cpython2.7-debug/Lib/test/test_sys.py", line 415, in test_43581
    self.assertTrue(sys.__stdout__.encoding == sys.__stderr__.encoding)
AssertionError: False is not true

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Can be reproduced by one of following commands:

$ ./python -m test.regrtest -v test_sys | cat
$ ./python -m test.regrtest -v test_sys 2>/dev/null

Proposed patch fixes the test.