Broken nightly builds
Two nights ago, the nightly builds failed, and notably Job #51860 (hg-5.2). I confirmed with a manual retry.
This comes as a surprise because it looks like the base image for Mercurial 5.2 hasn't changed in that time frame. Perhaps something depends on some external condition.
Fixing the CI is a high priority task in my book, I'll look at it ASAP.