Error printing tracebacks to StringIO stream on Python 3

[Gediminas Paulauskas]

subunit is used in zope.testrunner

It's test fail under Python 3(.4). Example:

Error in test test_print_failure_containing_utf8_bytestrings (zope.testrunner.tests.test_subunit.TestSubunitTracebackPrinting)
Traceback (most recent call last):
  File "/usr/lib/python3.4/unittest/case.py", line 57, in testPartExecutor
    yield
  File "/usr/lib/python3.4/unittest/case.py", line 570, in run
    self.setUp()
  File "/home/menesis/src/zope/zopetoolkit/trunk/src/zope.testrunner/.tox/py34/lib/python3.4/site-packages/zope/testrunner/tests/test_subunit.py", line 57, in setUp
    options, stream=self.output)
  File "/home/menesis/src/zope/zopetoolkit/trunk/src/zope.testrunner/.tox/py34/lib/python3.4/site-packages/zope/testrunner/formatter.py", line 790, in __init__
    self._subunit = subunit.TestProtocolClient(self._stream)
  File "/home/menesis/src/zope/zopetoolkit/trunk/src/zope.testrunner/python_subunit-0.0.18-py3.4.egg/subunit/__init__.py", line 621, in __init__
    stream = make_stream_binary(stream)
  File "/home/menesis/src/zope/zopetoolkit/trunk/src/zope.testrunner/python_subunit-0.0.18-py3.4.egg/subunit/__init__.py", line 1294, in make_stream_binary
    return _unwrap_text(stream)
  File "/home/menesis/src/zope/zopetoolkit/trunk/src/zope.testrunner/python_subunit-0.0.18-py3.4.egg/subunit/__init__.py", line 1313, in _unwrap_text
    return stream.buffer
AttributeError: '_io.StringIO' object has no attribute 'buffer'

[Robert Collins (lifeless)]

So, I'm a bit uncomfortable with the patch - because we require the ability to write raw bytes to a stream - and _io.StringIO will not accept raw bytes. What zope's own tests should be doing is something like:

bytestream = io.BytesIO()
stringstream = io.TextIOWrapper(bytestream, "utf8")
# now you can do string operations on stringstream and byte operations on bytestream.

which will work on all pythons from 2.6 through 3.4 and pypy.

[Robert Collins (lifeless)]

Ok, looking at this again, its really appropriate to fail. Subunit needs a binary stream. Either pass one in, or pass something that can be unwrapped in.