Please bump this from the existing (very old) version in the Gentoo Portage tree 1.0.8 to upstream 1.4.2. I have tested this by renaming the ebuild with no other changes, and 1.4.2 builds without any errors.
Done in commit daa027ef1e0fad380a290c5bcae6c864e50ccda3 Author: Matthew Thode <prometheanfire@gentoo.org> Date: Wed May 20 11:13:26 2020 -0500 dev-python/alembic: 1.4.2 bump Package-Manager: Portage-2.3.99, Repoman-2.3.22 Signed-off-by: Matthew Thode <prometheanfire@gentoo.org>