This gets us Python 3.8, in tree since 9th May. We could instead do 5.7 (in tree since 3rd July).
We usually stick with versions in stable that correspond to LTS kernel releases. So in this case we either need to add python3_8 support to btrfs-progs-5.4.1 or we wait for the forthcoming btrfs-progs-5.9 (assuming that 5.9 will be the next LTS kernel series).
Unable to check for sanity: > no match for package: sys-fs/btrfs-progs-5.6.1
All sanity-check issues have been resolved
Hmm. I guess we do 5.10 when it's out.
*** This bug has been marked as a duplicate of bug 758317 ***