Fix ENOTSOCK traceback when iopub socket closes during shutdown (#1518) #4093

Job	Run time
test_without_debugpy (ubuntu-latest, 3.10)	2m 25s
Test Prereleases	2m 35s
Test Minimum Versions	2m 38s
Test Lint	1m 9s
link_check	3m 56s
test_docs	46s
Make SDist	26s
check_release	1m 48s
build (ubuntu-latest, qt6, 3.11)	2m 40s
build (ubuntu-latest, qt6, 3.12)	2m 50s
build (ubuntu-latest, qt6, 3.10)	2m 53s
build (ubuntu-latest, qt5, 3.14)	2m 36s
build (ubuntu-latest, qt6, 3.13)	2m 40s
build (ubuntu-latest, qt5, 3.10)	2m 46s
build (windows-latest, qt5, 3.10)	4m 27s
build (windows-latest, qt6, 3.11)	3m 26s
build (ubuntu-latest, qt5, pypy-3.11)	3m 26s
build (windows-latest, qt6, pypy-3.11)	9m 34s
build (windows-latest, qt5, 3.14)	4m 21s
build (macos-latest, qt5, 3.10)	3m 36s
build (macos-latest, qt6, pypy-3.11)	4m 37s
build (windows-latest, qt6, 3.13)	4m 14s
build (windows-latest, qt6, 3.10)	4m 29s
build (macos-latest, qt6, 3.10)	3m 17s
build (windows-latest, qt6, 3.12)	3m 55s
build (macos-latest, qt6, 3.11)	3m 24s
build (macos-latest, qt6, 3.13)	3m 15s
build (macos-latest, qt5, pypy-3.11)	4m 41s
build (macos-latest, qt5, 3.14)	2m 32s
build (windows-latest, qt5, pypy-3.11)	7m 46s
build (ubuntu-latest, qt6, pypy-3.11)	3m 25s
build (macos-latest, qt6, 3.12)	2m 35s
Install from SDist and Test	2m 30s
coverage	11s
	1h 51m 49s

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