Download sandbox from s3 to scheduler

[cmsdmwmbot]

Jenkins results:

• Python3 Pylint check: succeeded
  • 3 comments to review
• Pycodestyle check: succeeded
  • 34 comments to review

Details at https://cmssdt.cern.ch/dmwm-jenkins/view/All/job/DMWM-CRABServer-PR-test/2203/artifact/artifacts/PullRequestReport.html

[novicecpp]

Go Go :rocket: :rocket: And thanks for fixing pylint :bowing_man:

[belforte]

tested, OK.