v0.18.0 is mostly a bugfix release: https://github.com/meejah/txtorcon/releases/tag/v0.18.0 v0.19.0 is a major update https://github.com/meejah/txtorcon/releases/tag/v0.19.0
Since this package is marked as maintainer-needed and nothing in the tree depends on it, you might consider treecleaning. grep -r txtorcon --include=\*.ebuild /var/portage/tree net-libs/txtorcon/txtorcon-0.13.0.ebuild:HOMEPAGE="https://github.com/meejah/txtorcon https://pypi.python.org/pypi/txtorcon"
commit 49470e4bb06c36e90c4e45cd611906e9f44de731 Author: Michał Górny <mgorny@gentoo.org> AuthorDate: Mon Aug 14 09:39:45 2017 Commit: Michał Górny <mgorny@gentoo.org> CommitDate: Mon Aug 14 09:47:19 2017 net-libs/txtorcon: Remove last-rited pkg, #616550 net-libs/txtorcon/Manifest | 1 - net-libs/txtorcon/metadata.xml | 9 --------- net-libs/txtorcon/txtorcon-0.13.0.ebuild | 30 ------------------------------ profiles/package.mask | 5 ----- 4 files changed, 45 deletions(-)