(hmm, my previous reply got lost?)
Sorry about that Martin, we did not know Cockpit was using those interfaces. We use double-underscore prefixed symbols to indicate interfaces for PCP internal use - and as you found in PCP v4 some of these have moved and/or changed.
It's fortunate that it seems to only affect test code in Cockpit (and builds, of course - so far from ideal) - but at least it should not be an issue for end users. I've audited Cockpit sources and sent through a couple of PRs to ensure Cockpit now only uses officially supported PMAPI interfaces.