test fails with Unicode problem

Python 2.6.5 with testtools 0.9.4

 * Testing of dev-python/testtools-0.9.4 with CPython 2.6...
Tests running...
Ran 145 tests in 0.076s

OK
Traceback (most recent call last):
  File "/usr/lib/python2.6/runpy.py", line 122, in _run_module_as_main
    "__main__", fname, loader, pkg_name)
  File "/usr/lib/python2.6/runpy.py", line 34, in _run_code
    exec code in run_globals
  File "/var/tmp/portage/dev-python/testtools-0.9.4/work/testtools-0.9.4/testtools/run.py", line 282, in <module>
    program = TestProgram(argv=sys.argv, testRunner=runner)
  File "/var/tmp/portage/dev-python/testtools-0.9.4/work/testtools-0.9.4/testtools/run.py", line 134, in __init__
    self.runTests()
  File "/var/tmp/portage/dev-python/testtools-0.9.4/work/testtools-0.9.4/testtools/run.py", line 274, in runTests
    self.result = testRunner.run(self.test)
  File "/var/tmp/portage/dev-python/testtools-0.9.4/work/testtools-0.9.4/testtools/run.py", line 42, in run
    return test.run(result)
  File "/usr/lib/python2.6/unittest.py", line 460, in run
    test(result)
  File "/usr/lib/python2.6/unittest.py", line 464, in __call__
    return self.run(*args, **kwds)
  File "/usr/lib/python2.6/unittest.py", line 460, in run
    test(result)
  File "/usr/lib/python2.6/unittest.py", line 464, in __call__
    return self.run(*args, **kwds)
  File "/usr/lib/python2.6/unittest.py", line 460, in run
    test(result)
  File "/usr/lib/python2.6/unittest.py", line 464, in __call__
    return self.run(*args, **kwds)
  File "/usr/lib/python2.6/unittest.py", line 460, in run
    test(result)
  File "/usr/lib/python2.6/unittest.py", line 300, in __call__
    return self.run(*args, **kwds)
  File "testtools/testcase.py", line 380, in run
    return self.__RunTest(self, self.exception_handlers).run(result)
  File "testtools/runtest.py", line 67, in run
    return self._run_one(actual_result)
  File "testtools/runtest.py", line 81, in _run_one
    return self._run_prepared_result(ExtendedToOriginalDecorator(result))
  File "testtools/runtest.py", line 100, in _run_prepared_result
    handler(self.case, self.result, e)
  File "testtools/testcase.py", line 348, in _report_error
    result.addError(self, details=self.getDetails())
  File "testtools/testresult/real.py", line 397, in addError
    return self.decorated.addError(test, details=details)
  File "testtools/testresult/real.py", line 66, in addError
    self._err_details_to_string(test, err, details)))
  File "testtools/testresult/real.py", line 131, in _err_details_to_string
    return _details_to_str(details)
  File "testtools/testresult/real.py", line 569, in _details_to_str
    return _u(''.join(chars))
  File "testtools/compat.py", line 53, in _u
    .replace("\\\\U", "\\U").decode("unicode-escape"))
UnicodeDecodeError: 'unicodeescape' codec can't decode bytes in position 1748-1750: truncated \UXXXXXXXX escape