According to https://github.com/pimutils/vdirsyncer/releases there's a new version.
Thank you for the bump request. You can help the maintainer with further information: Does a simple bump [1] work on your system? Chances are high, because a first look on the bump revealed only small changes. [1] https://wiki.gentoo.org/wiki/Custom_repository#Simple_version_bump_of_an_ebuild_in_the_local_overlay
A simple bump works. In fact, not so simple : you must use the github package url : http://cgit.thetys-retz.net/overlay/commit/?id=85bf3ca3139f90084573a5560850099a7b110473
commit 1bfa1307204e189091b66b385181d94a50da5c07 Author: Amy Liffey <amynka@gentoo.org> Date: Sat Jul 8 21:03:30 2017 +0200 dev-python/vdirsyncer: version bump 0.16.0 bug #623748 Thank you for testing!