Comment 2 for bug 1865209

Upstream has now merged the change to support python3 as a component. This will release in Boost 1.73, but it's a small patch and should be possible to backport to 1.71:

https://github.com/boostorg/boost_install/commit/7d2b3bf3a25ecce33e256370e47d776d75685f7e