I had the same error today. Managed to solve it by installing the newest available version of Python (which is used by Calibre). You can find the newest version of Python on their official website (link is for Windows users):
https://www.python.org/downloads/windows/
(I did not uninstall/reinstall Calibre before updating Python so didn't have to reconfigure anything)
Hope this helps some people who encounter this nasty python error
