Merge pull request #18589 from dannon/import-type-enforcement #1022

Job	Run time
build-client / build-client	27s
setup-selenium / setup_chromedriver	5s
Test (3.8, 0)	40m 21s
Test (3.8, 1)	50m 14s
Test (3.8, 2)	49m 13s
	2h 20m 20s

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