[RHEL8] use python3 instead of python2 which is not available

[smuzaffar]

To migrate away from python2 dependency

[smuzaffar]

please test

[cmsbuild]

A new Pull Request was created by @smuzaffar (Malik Shahzad Muzaffar) for branch IB/CMSSW_12_4_X/master.

@smuzaffar, @iarspider can you please review it and eventually sign? Thanks.
@perrotta, @dpiparo, @qliphy you are the release manager for this.
cms-bot commands are listed here

[smuzaffar]

test parameters:

• full_cmssw = true

[smuzaffar]

please test for rhel8_amd64_gcc10

[cmsbuild]

+1

Summary: https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-f1911b/23241/summary.html
COMMIT: 9f5d14a
CMSSW: CMSSW_12_4_X_2022-03-20-2300/slc7_amd64_gcc10
User test area: For local testing, you can use /cvmfs/cms-ci.cern.ch/week1/cms-sw/cmsdist/7703/23241/install.sh to create a dev area with all the needed externals and cmssw changes.

Comparison Summary

@slava77 comparisons for the following workflows were not done due to missing matrix map:

• /data/cmsbld/jenkins/workspace/compare-root-files-short-matrix/data/PR-f1911b/39434.911_TTbar_14TeV+2026D88_DD4hep+TTbar_14TeV_TuneCP5_GenSimHLBeamSpot14+DigiTrigger+RecoGlobal+HARVESTGlobal

Summary:

• No significant changes to the logs found
• Reco comparison results: 0 differences found in the comparisons
• DQMHistoTests: Total files compared: 49
• DQMHistoTests: Total histograms compared: 3695650
• DQMHistoTests: Total failures: 51284
• DQMHistoTests: Total nulls: 66
• DQMHistoTests: Total successes: 3644278
• DQMHistoTests: Total skipped: 22
• DQMHistoTests: Total Missing objects: 0
• DQMHistoSizes: Histogram memory added: 0.0 KiB( 48 files compared)
• Checked 204 log files, 45 edm output root files, 49 DQM output files
• TriggerResults: no differences found