File:

%! TEX program = pdflatex
\documentclass{memoir}
\begin{document}
\fixpdflayout
\end{document}

In the log there is:

Class memoir Warning: As of 2018, \fixpdflayout\ is no longer used on input line 4.

But no error is reported.

(This is similar to

  setlocal errorformat+=%+WPackage\ %.%#\ Warning:\ %m\ on\ input\ line\ %l.

format but it's Class instead of Package, I think.)

(I have no idea what the command is for, just to demonstrate the issue.)