Alternative `format_source` fix #31125

Job	Run time
build-client / build-client	10m 15s
setup-selenium / setup_chromedriver	4s
Test (3.8, 0)	25m 59s
Test (3.8, 1)	25m 57s
Test (3.8, 2)	25m 56s
	1h 28m 11s

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