[PR #13548/48be3c8b backport][8.4.x] Fix test_doctest_unexpected_exception

[patchback]

This is a backport of PR #13548 as merged into main (48be3c8).

Fixes #13547.

I've corrected the expected message based on the output of 3.14 but I haven't actually tracked down whether this is expected in 3.14 or why.
 

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