Build failure in installed-tests job
The following failure occurs only on the installed-tests job:
autoreconf: running: /usr/bin/autoconf --force
configure.ac:134: error: possibly undefined macro: AC_MSG_WARN
If this token and others are legitimate, please use m4_pattern_allow.
See the Autoconf documentation.
autoreconf: /usr/bin/autoconf failed with exit status: 1
AC_MSG_WARN
is defined as part of Autoconf, so what the error message says is probably not the problem.
I don't believe this code has changed recently, and it's not reproduced on other job.