Periodically, people report issues like #11891 when trying to use Twisted on Windows. There are two problems here.

The first is that our CI pipeline for twisted-iocpsupport should be more proactive and produce extension modules for all configurations that a Windows user might encounter.

However, we are never going to be able to be completely comprehensive there, and thus we should make it so that pip install twisted can function as a pure-python package on Windows as it does on other platforms. So while we should make pip install twisted[all] work well by doing the first thing, we should also do this.