Site is down after Pelican upgrade. From the error message, the
StackOvermind (https://stackoverflow.com/a/57479744) suggests that the
Markdown library needs a bump, too. (Um, should I be doing anything
about all the other packages? I can see why people like even Pipenv,
if the alternative is a flat requirements.txt ...)
We also got a warning from nuPelican about %-formatting in one
setting.