This bug was causing the zstd entry under "Available Compression Engines" to
be omitted from the documentation for some versions of python3. I could
upgrade, but past upgrades have broken venvs and clobbered installed packages.
It's a trivial workaround, so there's no sense in leaving this subtle issue. It
was flushed out by changing the module policy here from 'allow' to 'c', and
seeing this error:
ImportError: DLL load failed while importing parsers: The parameter is incorrect.