Ahem. I promise I did test it, but then testing on developers’ machines is notoriously untrustworthy. In short, I failed to include the versioning module in the winshell sdist. Several fumbled attempts and struggles with PyPI later, I bring you: winshell 0.5.4 whose sole purpose is to fix this problem.
Many thanks to Steve Reiss who took the trouble to let me know it was failing to install