Automated cherry pick of #2109: changed package name to flake8 to fix pip install

[tenzen-y]

Cherry pick of #2109 on v1.8-branch.
#2109: changed package name to flake8 to fix pip install
For details on the cherry pick process, see the cherry pick requests page.

I stole the commit since #2109 was not signed in CLA...

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[coveralls]

Pull Request Test Coverage Report for Build 9419963963

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 2 unchanged lines in 1 file lost coverage.
• Overall coverage decreased (-0.02%) to 35.366%

---

Files with Coverage Reduction	New Missed Lines	%
pkg/controller.v1/mpi/mpijob_controller.go	2	80.48%

Totals
Change from base Build 8869266420:	-0.02%
Covered Lines:	4372
Relevant Lines:	12362

---

💛 - Coveralls

[andreyvelich]

Thank you @tenzen-y!
/lgtm
/approve

[google-oss-prow]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: andreyvelich

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