microtype error with lualatex: "attempt to call field warning a nil value"

Question

no answer needed, I'm adding the question as reference

After todays update of luaotfload microtype gives an error when used with lualatex:

\documentclass{article}

\usepackage{microtype}

\begin{document}
abc

\end{document}

leads to

/tex/latex/microtype/microtype.lua:145: attempt to call field 'warning' (a nil v
alue)
stack traceback:
    ...exlive/2018/texmf-dist/tex/latex/microtype/microtype.lua:145: in main chunk
    [C]: in function 'require'
    [\directlua]:1: in main chunk.
l.59 \MT@lua{require("microtype")}

Answer 1

This is due to a bug in microtype. It uses an undefined lua-function, the bug appears now due as a side-effect of some changes in luaotfload.

A work-around until microtype is fixed is to load luatexbase:

\documentclass{article}
\usepackage{luatexbase}
\usepackage{microtype}

\begin{document}
abc

\end{document}