Sybil causing unit test failures.

[clpetix]

Sybil is not acknowledging skip: start if(gsd == None, reason="gsd not installed") which is causing tests in the Snapshot's examples to fail. This seems to be related to the recent change in pytest from 8.4.2 to 9.0.0.

[clpetix]

This seems to be a bigger issue with pytest not working with unittest.SkipTest as described in this issue on their repository.

@mphoward, they have a PR open to deal with this, but I think we could probably pin v8 of pytest and unpin once they work out the issues.

[mphoward]

Thanks! Yes, please pin a version. Do you need it to be specifically one version, or just <=?

[nicoddemus]

I suggest pinning to !=9.0.0, so no change will be necessary once 9.0.1 releases.