Python 2 reached upstream end-of-life in January 2020. In Fedora Rawhide, it's now provided from the compat package `python27`. Packages that only use Python 2 at build time, like openmsx, had a general exception to keep using it in Fedora 31. Now, the dependency should be removed. It seems that Python 3 support was already merged upstream: https://github.com/openMSX/openMSX/commit/7e0f3f15fd229b2b7efa7ad179beffe9f25c2321 If it's possible that the Python 2 build dependency won't get removed in Fedora 33, please let us know; the package will need a FESCo exception. If you need anything from us, or something is unclear, please mention it here.
I've changed the pkg to use python3 for building and committed and build openmsx-0.15.0-5.fc33 using python3, closing.
Thank you!