with latest TL update and running lualatex
documentclass{article}
\usepackage{fontspec}
\setmainfont{Linux Libertine O}
\begin{document}
foo
\end{document}
[...]
(/usr/local/texlive/2015/texmf-dist/tex/latex/fontspec/fontspec.cfg)))
! Undefined control sequence.
<argument> \xetex_suppressfontnotfounderror:D
l.3 \setmainfont{Linux Libertine O}
Herbert