The cfa changes (just better handling the traceback from exceptions) were an accidental spill over, but they might as well get reviewed here!

Hi @davidhassell, the CI jobs look like they are hanging here (over 4 hours runtime) so I suggest cancelling them. I have seen these tests hanging recently and need to investigate that, and given that a few have passed enough for us to be confident this is good along with a local full-suite pass, it seems highly unlikely they are hanging due to this PR. So I'll ignore the CI in my reviewing. Thanks.

Hi Sadie, the CI jobs had finally dies by the time a looked )or perhaps you killed them?). I must confess to usually running the tests individually these days, as I still get sporadic hanging - and they passed in this way for me on this PR. Do you think that moving to pytest might be helpful in solving this issue? I don't have any evidence for this, other than it's different to unittest! It's a bigger job, but something that could be nice in the longer term. That's a discussion for elsewhere, anyway.

I must confess to usually running the tests individually these days, as I still get sporadic hanging - and they passed in this way for me on this PR.

Ah, sorry about this and the inconvenience. Something is up and it may just be in the Actions infrastructure. Once the machine and performance release is out, maybe I can briefly investigate.

Do you think that moving to pytest might be helpful in solving this issue? I don't have any evidence for this, other than it's different to unittest! It's a bigger job, but something that could be nice in the longer term. That's a discussion for elsewhere, anyway.

I think that is much more likely to be about some specific issue(s) with the codebase or underlying C libraries rather than the test framework used, but I think moving to pytest would be a good idea anyway, e.g. we can parametrise the test methods very easily and cleanly, as you are probably aware. So definitely keep that flagged for the future (in your mind or you could even open up an Issue if one isn't already there).

This is good to go so I will merge, just to tie up loose ends before the weekend...