Gentoo repository contains old icalendar 3.x. Fourth version exists and some packages such as app-misc/khal requires it.
The bug has been referenced in the following commit(s): https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=c905dae24d3f2fdd01f38cf3998275601f2ce77f commit c905dae24d3f2fdd01f38cf3998275601f2ce77f Author: Karel Kočí <cynerd@email.cz> AuthorDate: 2018-12-04 21:37:24 +0000 Commit: Michał Górny <mgorny@gentoo.org> CommitDate: 2018-12-09 08:44:59 +0000 dev-python/icalendar: update to version 4.0.3 Bug: https://bugs.gentoo.org/672530 Signed-off-by: Karel Kočí <cynerd@email.cz> Closes: https://github.com/gentoo/gentoo/pull/10572 Signed-off-by: Michał Górny <mgorny@gentoo.org> dev-python/icalendar/Manifest | 1 + dev-python/icalendar/icalendar-4.0.3.ebuild | 46 +++++++++++++++++++++++++++++ 2 files changed, 47 insertions(+)