PR #2527 suggests "making failing tests more strict about failing
gracefully".
To achive this, make meson exit with distinct exit statuses for meson errors
and python exceptions, and check the exit status is as expected for failing
tests.
I can't see how to write a test for this, within the current framework.
You can test this change by reverting the fix (but not the test) from commit
1a159db8 and verifying that 'test cases/failing/66 string as link target'
fails.
This allows us to more easily have the documentation in sync with
the source code as people will have to document new features etc
right at the time where they implement it.