Use displayException instead of show for showing exceptions

[adamgundry]

Here's my proposed resolution to #327. By calling displayException instead of show we get prettier exception output for any exception type that implements displayException, including tasty's version of HUnitFailure. (Unfortuntately HUnit's version of HUnitFailure doesn't currently implement displayException, but that's a HUnit issue.)

[andreasabel]

Why doesn't this run through CI?

[adamgundry]

I'm not sure if it is to do with my having opened a branch from a fork? Or is it perhaps that Travis CI now requires applying for credits for open source projects?

[andreasabel]

Yeah, Travis is dead, but there is a GHA CI now: https://github.com/UnkindPartition/tasty/blob/16289a77495eb8279c5e544886ef52503becd148/.github/workflows/ci.yaml
Maybe it is misconfigured, it says on: [push] where I usually see on: [push, pull_request] or some refinement of this.
Ping @UnkindPartition.

[andreasabel]

@adamgundry : I updated the CI triggers. Can you please rebase this onto master and force-push, to see if CI runs now?

[adamgundry]

Thanks @andreasabel, looks like it is indeed running now.

[Bodigrim]

@andreasabel @VictorCMiraldo @martijnbastiaan this looks good to me, any more opinions?

[martijnbastiaan]

LGTM. A changelog entry would make sense.

[VictorCMiraldo]

LGTM to me too!

[Bodigrim]

I've updated changelogs, rebased and merged. Thanks, @adamgundry!

[edsko]

In case anyone else runs into this: if the exception is raised in a QuickCheck test, the exception is shown in QuickCheck itself, and not in tasty or tasty-quickcheck. I've opened a similar PR for QuickCheck itself at nick8325/quickcheck#417 .