py2 cleanup: fastjet and mxnet-predict build with py3

[smuzaffar]

FYI @davidlange6

[smuzaffar]

please test

[cmsbuild]

A new Pull Request was created by @smuzaffar (Malik Shahzad Muzaffar) for branch IB/CMSSW_12_0_X/master.

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

[cmsbuild]

Pull request #7087 was updated.

[smuzaffar]

please test

[cmsbuild]

+1

Summary: https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-803ec5/16397/summary.html
COMMIT: 0a4f968
CMSSW: CMSSW_12_0_X_2021-07-01-1100/slc7_amd64_gcc900
User test area: For local testing, you can use /cvmfs/cms-ci.cern.ch/week1/cms-sw/cmsdist/7087/16397/install.sh to create a dev area with all the needed externals and cmssw changes.

The following merge commits were also included on top of IB + this PR after doing git cms-merge-topic:

• remove pyminuit and its dependencies #7081 @davidlange6: remove pyminuit and its dependencies

You can see more details here:
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-803ec5/16397/git-recent-commits.json
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-803ec5/16397/git-merge-result

Comparison Summary

Summary:

• No significant changes to the logs found
• Reco comparison results: 4 differences found in the comparisons
• DQMHistoTests: Total files compared: 38
• DQMHistoTests: Total histograms compared: 2785711
• DQMHistoTests: Total failures: 6
• DQMHistoTests: Total nulls: 1
• DQMHistoTests: Total successes: 2785682
• DQMHistoTests: Total skipped: 22
• DQMHistoTests: Total Missing objects: 0
• DQMHistoSizes: Histogram memory added: -0.004 KiB( 37 files compared)
• DQMHistoSizes: changed ( 312.0 ): -0.004 KiB MessageLogger/Warnings
• Checked 160 log files, 37 edm output root files, 38 DQM output files
• TriggerResults: no differences found

[smuzaffar]

+externals
comparison diffs are due to message logger output

[cmsbuild]

This pull request is fully signed and it will be integrated in one of the next IB/CMSSW_12_0_X/master IBs (tests are also fine). This pull request will now be reviewed by the release team before it's merged. @silviodonato, @dpiparo, @qliphy (and backports should be raised in the release meeting by the corresponding L2)