If you run test_warnings.py under an ascii terminal (at least on Mac OS X) then test_warnings.CEnvironmentVariableTests.test_nonascii fails. Perhaps the test should be skipped? 

======================================================================
FAIL: test_nonascii (__main__.CEnvironmentVariableTests)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "Lib/test/test_warnings.py", line 758, in <module>
    test_main()
  File "Lib/test/test_warnings.py", line 753, in test_main
    PyEnvironmentVariableTests
  File "/compile/python-trunk3/Lib/test/support.py", line 1053, in run_unittest
    _run_suite(suite)
  File "/compile/python-trunk3/Lib/test/support.py", line 1027, in _run_suite
    result = runner.run(suite)
  File "/compile/python-trunk3/Lib/unittest/runner.py", line 158, in run
    result.printErrors()
  File "/compile/python-trunk3/Lib/unittest/runner.py", line 109, in printErrors
    self.printErrorList('FAIL', self.failures)
  File "/compile/python-trunk3/Lib/unittest/runner.py", line 116, in printErrorList
    self.stream.writeln("%s" % err)
  File "/compile/python-trunk3/Lib/unittest/runner.py", line 24, in writeln
    self.write(arg)
UnicodeEncodeError: 'ascii' codec can't encode character '\xf3' in position 121: ordinal not in range(128)


Looks like the traceback here actually comes from unittest trying to report the failure.