UnicodeEncodeError when raising an exception with non-ascii characters

[anthonywee]

The Python 2.6 tests will fail with a UnicodeEncodeError if an exception is raised with non-ascii characters in the message.

For example, I updated the test_non_flaky_thing() test in test_example.py to include the non-ascii message in the exception:

@genty
class ExampleFlakyTestsWithUnicodeTestNames(ExampleFlakyTests):
    @genty_dataset('ascii name', 'ńőń ȁŝćȉȉ ŝƭȕƒƒ')
    def test_non_flaky_thing(self, message):
        self._threshold += 1
        if self._threshold < 1:
            raise Exception(
                "Threshold is not high enough: {0} vs {1} for '{2}'.".format(
                    self._threshold, 1, message),
            )

This caused a UnicodeEncodeError when running the Python 2.6 tests:

py26 runtests: PYTHONHASHSEED='2117695302'
py26 runtests: commands[0] | nosetests --with-flaky --exclude=pytest|test_options_example
....................................
===Flaky Test Report===

Traceback (most recent call last):
  File ".tox/py26/bin/nosetests", line 11, in <module>
    sys.exit(run_exit())
  File "/Users/awee/open_source/flaky_fork/flaky/.tox/py26/lib/python2.6/site-packages/nose/core.py", line 121, in __init__
    **extra_args)
  File "/System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/unittest.py", line 817, in __init__
    self.runTests()
  File "/Users/awee/open_source/flaky_fork/flaky/.tox/py26/lib/python2.6/site-packages/nose/core.py", line 207, in runTests
    result = self.testRunner.run(self.test)
  File "/Users/awee/open_source/flaky_fork/flaky/.tox/py26/lib/python2.6/site-packages/nose/core.py", line 66, in run
    result.printErrors()
  File "/Users/awee/open_source/flaky_fork/flaky/.tox/py26/lib/python2.6/site-packages/nose/result.py", line 110, in printErrors
    self.config.plugins.report(self.stream)
  File "/Users/awee/open_source/flaky_fork/flaky/.tox/py26/lib/python2.6/site-packages/nose/plugins/manager.py", line 99, in __call__
    return self.call(*arg, **kw)
  File "/Users/awee/open_source/flaky_fork/flaky/.tox/py26/lib/python2.6/site-packages/nose/plugins/manager.py", line 167, in simple
    result = meth(*arg, **kw)
  File "/Users/awee/open_source/flaky_fork/flaky/flaky/flaky_nose_plugin.py", line 182, in report
    self._add_flaky_report(stream)
  File "/Users/awee/open_source/flaky_fork/flaky/flaky/_flaky_plugin.py", line 236, in _add_flaky_report
    stream.write(self._stream.getvalue())
UnicodeEncodeError: 'ascii' codec can't encode characters in position 760-762: ordinal not in range(128)
ERROR: InvocationError: '/Users/awee/open_source/flaky_fork/flaky/.tox/py26/bin/nosetests --with-flaky --exclude=pytest|test_options_example'
__________________________________________________________________________________ summary __________________________________________________________________________________
ERROR:   py26: commands failed