Handle libraries that fail to parse

[AnHeuermann]

Currently any tag that points to a Modelica library that fails to parse will trigger an exception in genindex and the Jenkins job will fail:

python -m ompackagemanager genindex
Traceback (most recent call last):
  File "/usr/lib/python3.10/runpy.py", line 196, in _run_module_as_main
    return _run_code(code, main_globals, None,
  File "/usr/lib/python3.10/runpy.py", line 86, in _run_code
    exec(code, run_globals)
  File "/var/lib/jenkins/ws/Update Package Index/ompackagemanager/__main__.py", line 67, in <module>
    main()
  File "/var/lib/jenkins/ws/Update Package Index/ompackagemanager/__main__.py", line 63, in main
    args.func()
  File "/var/lib/jenkins/ws/Update Package Index/ompackagemanager/genindex.py", line 127, in main
    raise Exception(firstKey + " " + refKey)
Exception: LEPSE v1.2.1

Instead we should send an e-mail to notify the package manager maintainers, mark the Jenkins job as unstable. Than exclude the tag from further processing but continue with the remaining packages.