We should probably try to add a call to variousRuggedCalls() between DumpManager.activate(dump) and Assert.fail("an exception should have been thrown"). This way, we really try to write, we don't only open the file.
The problem seems linked to the fact the CI runs the tests under root account, which
can bypass restricted files permissions. Running the test on a developer machine
under root gave me the same failure.
We have now to find if either we can get CI run tests with a less privileged account
or if we can set up a different strategy to ensure a write error is triggered and
detected.