In my goal of building calibre on core-updates, I encounter many build failures. The Python package graph seems to be extremely entangled, with dependencies on specific input package and even Python versions.
The only approach I could imagine is updating to newer versions, and this solved some of the build failures (but not all of them). I have pushed a few commits to core-updates. Please feel free to revert them if this is not the good approach. It would be nice if the Python team could take over, and more people joined the team :) Andreas