The current upstream version is 2.29. I had a build failure with the current Gentoo version (2.27) and locally did a trivial bump which seems to have solved the problem.
Please link a ticket to the build failure here. It is important to know, if the current package is broken.
Here you go: bug #695800.
The bug has been closed via the following commit(s): https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=69ba78f250365425de39008e24b4dbe2b13416ee commit 69ba78f250365425de39008e24b4dbe2b13416ee Author: David Seifert <soap@gentoo.org> AuthorDate: 2019-10-07 08:01:50 +0000 Commit: David Seifert <soap@gentoo.org> CommitDate: 2019-10-07 08:01:50 +0000 dev-python/graph-tool: Version bump to 2.29 * Remove support for Python 2.7 Closes: https://bugs.gentoo.org/695772 Package-Manager: Portage-2.3.76, Repoman-2.3.17 Signed-off-by: David Seifert <soap@gentoo.org> dev-python/graph-tool/Manifest | 1 + dev-python/graph-tool/graph-tool-2.29.ebuild | 79 ++++++++++++++++++++++++++++ 2 files changed, 80 insertions(+)