yaml.safe_load() has been deprecated in the latest versions of ruamel.yaml. We have fixed the issue in the main branch but this may still affect users of v4.0 if they set up a conda environment from scratch, since ruamel.yaml is not pinned in SKLL requirements.

We will fix the issue in the next release but in the meantime, users can mitigate the issue by downgrading ruamel.yaml to <0.18.0.