According to pylast page https://github.com/pylast/pylast, it should be compatible with Python 3.6, yet ebuild states compatibility with at most Python 3.5.
The bug has been closed via the following commit(s): https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=702c20499fa316fb9918ba98d11a2f9e993f0378 commit 702c20499fa316fb9918ba98d11a2f9e993f0378 Author: Tim Harder <radhermit@gentoo.org> AuthorDate: 2017-09-21 06:38:45 +0000 Commit: Tim Harder <radhermit@gentoo.org> CommitDate: 2017-09-21 06:38:45 +0000 dev-python/pylast: version bump to 1.9.0 Closes: https://bugs.gentoo.org/631508 dev-python/pylast/Manifest | 1 + dev-python/pylast/pylast-1.9.0.ebuild | 23 +++++++++++++++++++++++ 2 files changed, 24 insertions(+)