improved traces to debug a problem that only happens in ci (can't reproduce even when logged as jenkins-agent)

The error message is:
> ValueError: failed to find compilers/ifort/latest amongst available environment modules (set())

work related to [https://bugzilla.ipr.univ-rennes.fr/show_bug.cgi?id=3958]

ci/ipr.jenkins

@@ -31,6 +31,7 @@ pipeline {
                 sh """#!/bin/bash
                 set -o errexit
                 source /etc/profile.d/modules.sh
+                module avail
                 source ${IPRBENCH_VENV_PATH}/bin/activate &&
                 python -m unittest ./ci/test_iprcluster.py
                 """