Move to new version json schema reference resolution

[bpkroth]

The latest version 4.18.0 of jsonschema migrated to a new way of handling schema reference resolution that breaks our current code. Will need to adjust it, but for now I've pinned it to the old version in #436

See Also:
https://python-jsonschema.readthedocs.io/en/stable/referencing/#migrating-from-refresolver