if test "$RUN_VERY_EXPENSIVE_TESTS" != yes; then
  cat <<EOF >&2
$0: This test is very expensive, so it is disabled by default.
To run it anyway, rerun make check with the RUN_VERY_EXPENSIVE_TESTS
environment variable set to yes.  E.g.,

  env RUN_VERY_EXPENSIVE_TESTS=yes make check

EOF
  (exit 77); exit 77
fi
