I did not review the patches closely, but I did try to build core-image-full-cmdline with the tip of poky and these patches applied. Everything was fine until do_rootfs... I've attached the log.

Essentially, there are some bits of dnf and so on which are not ready for Python 3.7. We have dnf version 2.7.5, but the latest upstream release is 3.4.0 (with a 3.5.0 just 3 days ago). Not sure yet if that would have helped.