On
#parabola:

< lxo> fauno, thanks, new binaries in texlive-bin-libre
looking good; however, it says “WARNING: not recreating formats since
texlive-core has version ''” which is presumably caused by texlive-core
being absent, with texlive-core-libre installed in its stead. I suppose
things might fail because of the failure to recreate formats.
something to adjust in a future update...

texlive.install in post_upgrade() checks version of texlive-core
and recreates formats if it's from TexLive 2012. The warning is
misleading and probably harmless, while it should show version like
'2013.31589-1.2'.