dev-java/lucene-regex is a RDEPEND for dev-python/pylucene ( Bug#81416 ) Ebuild prepared and needs bug for submission to sunrise overlay and subsequently entering portage
Ebuild in the java-expiramental overlay (thanks Serkan). It uses an eclass for lucene-contrib packages. Needs to be bumped to version 2.4.0
https://overlays.gentoo.org/svn/proj/java/java-experimental/dev-java/lucene-regex/
See my comment in bug 81416.