Subshells implemented using tornado event loops on 6.x branch #3363

Job	Run time
Test Lint	56s
check_release	1m 44s
link_check	3m 29s
build (ubuntu-latest, 3.9)	5m 3s
Make SDist	23s
test_docs	36s
build (ubuntu-latest, 3.13)	4m 59s
Test Minimum Versions	2m 29s
build (windows-latest, 3.9)	8m 22s
Test Prereleases	2m 10s
test_without_debugpy (ubuntu-latest, 3.9)	2m 13s
build (windows-latest, 3.13)	8m 33s
build (macos-latest, 3.9)	5m 26s
build (macos-latest, 3.13)	4m 57s
build (ubuntu-latest, pypy-3.9)	4m 30s
build (macos-latest, 3.10)	4m 57s
build (ubuntu-latest, 3.11)	4m 50s
build (ubuntu-latest, 3.12)	5m 57s
Install from SDist and Test	2m 11s
coverage	13s
	1h 13m 58s

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