properly report invalid run_range in config

[belforte]

reference https://cms-talk.web.cern.ch/t/impossible-to-run-crab-jobs/33451/17

[cmsdmwmbot]

Jenkins results:

• Python3 Pylint check: failed
  • 4 warnings and errors that must be fixed
  • 1 warnings
  • 50 comments to review
• Pycodestyle check: succeeded
  • 99 comments to review

Details at https://cmssdt.cern.ch/dmwm-jenkins/view/All/job/DMWM-CRABClient-PR-test/1049/artifact/artifacts/PullRequestReport.html