Improved exception context

[cpelley]

Ensure that we can understand where an exception was actually raised.

Issues

• https://github.com/MetOffice/improver_suite/issues/2253

[SamGriffithsMO]

How does dask handle errors being raised currently?

I was thinking if we might want two separate cases:

1. Operational - pool any raised errors, run as much as possible, then raise them at the end of the task
2. Development - Raise errors as soon as they arise and end the task

[cpelley]

@SamGriffithsMO, indeed. I previously added the following fail_fast argument to the in-house scheduler to do just that (the in-house scheduler being what's used by EPP now).
Though I haven't yet explored with EPP what the best operational behaviour might be (we are far away from that yet). It could be that a fail_fast=True would be the more appropriate behaviour in both dev and oper scenarios now that we pass data in memory and intermediate steps are lost. That is, being able restart the task sooner could be the preferred choice in oper now - something to be decided.
Out of scope for this PR mind, but 👍 for raising.

[SamGriffithsMO]

👍