This means either that the bash minimum version needs upping to a patch level or that the test is actually flaky and both I and all of the CI got lucky when running it (i'm not actually sure if any of the CI actually ran this test or just skipped it - the test.regrtest output on CI is never verbose so I can't tell).

if i can't untangle bash versions, the other alternative is to just not bother with a shell based test for this as it is too complicated due to depending on exact behaviors of a shell testing an interactive feature in fake interactive mode.

changing the child process to just "raise KeyboardInterrupt" as is done in the equivalent Windows test is sufficient.