The ebuild seems to be missing SRC_URI arrows to rename the distfile: 1.5.5.tar.gz
commit ef67394b2cb1a1c3b0079be18850a3a7ae09737d Author: David Seifert <soap@gentoo.org> Date: Fri Jun 2 19:03:39 2017 +0200 dev-python/sphinxcontrib-blockdiag: [QA] Use proper distfile name Bug: https://bugs.gentoo.org/show_bug.cgi?id=619848