def handlerAndBytesIO():
    """
    Construct a 2-tuple of C{(StreamHandler, BytesIO)} for testing interaction
    with the 'logging' module.

    @return: handler and io object
    @rtype: tuple of L{StreamHandler} and L{io.BytesIO}
    """
    output = BytesIO()
    stream = output
    template = py_logging.BASIC_FORMAT
    if _PY3:
        stream = TextIOWrapper(output, encoding="utf-8", newline="\n")
    formatter = py_logging.Formatter(template)
    handler = py_logging.StreamHandler(stream)
    handler.setFormatter(formatter)
    return handler, output

    Construct a 2-tuple of C{(StreamHandler, BytesIO)} for testing interaction
    with the 'logging' module.

    @return: handler and io object
    @rtype: tuple of L{StreamHandler} and L{io.BytesIO}
    
stackoverflow/venv/lib/python3.6/site-packages/twisted/logger/test/test_stdlib.py