test failures on windows w/python 2.6

[Robert Collins]

======================================================================
FAIL: testtools.tests.test_testresult.TestNonAsciiResultsWithUnittest.test_unprintable_exception
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Text attachment: traceback
------------
Traceback (most recent call last):
  File "testtools\runtest.py", line 169, in _run_user
    return fn(*args, **kwargs)
  File "testtools\testcase.py", line 499, in _run_test_method
    return self._get_test_method()()
  File "testtools\tests\test_testresult.py", line 1240, in test_unprintable_exception
    textoutput)
  File "testtools\testcase.py", line 275, in assertIn
    needle in haystack, '%r not in %r' % (needle, haystack))
AssertionError: 'UnprintableError: <unprintable UnprintableError object>\n' not in 'E\n=============
=========================================================\nERROR: test_unprintable_exception.Test.ru
nTest\n----------------------------------------------------------------------\n_StringException: Tex
t attachment: traceback\n------------\nTraceback (most recent call last):\n File "testtools\\runtes
t.py", line 169, in _run_user\n return fn(*args, **kwargs)\n File "testtools\\testcase.py", line
 499, in _run_test_method\n return self._get_test_method()()\n File "c:\\users\\jameinel\\appdat
a\\local\\temp\\TestNonAsciiResultsWithUnittest6rm7fc\\test_unprintable_exception.py", line 11, in r
unTest\n raise UnprintableError\nUnprintableError\n------------\n\n\n----------------------------
------------------------------------------\nRan 1 test in 0.001s\n\nFAILED (errors=1)\n'
------------

sometimes testtools.tests.test_testresult.TestNonAsciiResults.test_unprintable_exception fails too

[Robert Collins (lifeless)]

John Meinel says that python2.5 works fine.

[Martin Packman (gz)]

Have a hunch this might be twisted tests interfering somehow, but as I wrote the one that's failing I would say that wouldn't I.

[Martin Packman (gz)]

The blame here is a misguided BaseException.__unicode__ method added in Python 2.6 :
<http://bugs.python.org/issue2517>

This was then backed out again for 2.6.5:
<http://bugs.python.org/issue6108>

This test just needs stringification to fail, so providing its own unicode method avoids this incompatibility.