Unicode character causing error with bdist_wininst on python 3 but not python 2

Question

I'm compiling windows installers for my python code. I mostly write language-related tools and include examples that require utf-8 strings in my documentation, including the README file.

I'm slowly moving from Python 2 to Python 3 and recently found that the command

python setup.py bdist_wininst

works fine with python 2 but not for python 3.

I've traced the problem to the inclusion of unicode in my readme file. The readme file gets read into setup.py.

The bug occurs in Python36\lib\distutils\command\bdist_wininst.py

The error is: UnicodeEncodeError: 'mbcs' codec can't encode characters in position 0--1: invalid character

In python 2.7 the relevant code in bdist_wininst.py is

    if isinstance(cfgdata, str):
        cfgdata = cfgdata.encode("mbcs")

In python 3.6 the equivalent code in bdist_wininst.py is

    try:
        unicode
    except NameError:
        pass
    else:
        if isinstance(cfgdata, unicode):
            cfgdata = cfgdata.encode("mbcs")

Here is my readme file: https://github.com/timmahrt/pysle/blob/master/README.rst

And here is my setup.py file that reads in the README file https://github.com/timmahrt/pysle/blob/master/setup.py

And the relevant line from setup.py:

long_description=codecs.open('README.rst', 'r', encoding="utf-8").read()

My question: Is there a way to make python 3 happy in this case?