Because of an unintended interaction between a python-related eclass and the app-office/libreoffice ebuilds (any version), merging recently self-generated (see below for exact timeframe) libreoffice binary packages can fail to install with the error
* ERROR: app-office/libreoffice-18.104.22.168::gentoo failed (setup phase):
* PYTHON_CFLAGS is invalid for python-r1 suite, please take a look @ https://wiki.gentoo.org/wiki/Project:Python/Python.eclass_conversion#PYTHON_CFLAGS
The problem is fixed now, but any libreoffice binary packages generated with a portage tree from Fri Jan 2 00:15:15 2015 UTC to Sun Jan 4 22:18:12 2015 UTC will fail to reinstall. Current recommendation is to delete the self-generated binary package and re-install libreoffice from sources (or use libreoffice-bin).
This does NOT affect app-office/libreoffice-bin.
Updates may be posted here or on bug 534726. Happy heating. At least it's winter.