Markdown causing TypeError: expected string or buffer

[chrisspen]

After adding a long_description containing Markdown (per the method outlined the docs) to my package's setup.py, and twine is now unable to upload my package, and returns the error:

$ twine upload dist/criticalpath-0.1.4.tar.gz
Uploading distributions to https://upload.pypi.org/legacy/
TypeError: expected string or buffer

This sounds similar to this issue, but all the suggestions are to update package versions, which I've done to no effect.

Since the only change I made was to add a long_description, I presume that's the cause of the error, but I can find no fault in my string usage, and there's no traceback provided.

My versions:

$ twine --version
twine version 1.9.1 (pkginfo: 1.4.1, requests: 2.18.2, setuptools: 36.2.5,
requests-toolbelt: 0.8.0, tqdm: 4.15.0)
$ python --version
Python 3.5.2

[chrisspen]

I spoke too soon. Double checking my twine versions, I realize my global twine install (1.9.1) was overriding my local virtualenv twine install (1.11.0). Uninstalling the 1.9.1 forced it to use the more recent 1.11.0 version, which does not produce the error.