pywin32 won't install with Python 3.9 + Windows

[RudolfCardinal]

Likely third-party dependency problem: Installation fails under Windows 10 + Python 3.9.7 + pip 21.2.3 because pywin32 is reported by pip to be unavailable (in any version). The pywin32 page (https://pypi.org/project/pywin32/) reports Python 3.9 support, however. Ideal long-term solution is probably Docker, to save all this mess! (Works fine with Windows 10 + Python 3.8.10 + pip 21.1.1.)