Failing nightly build since Friday

FYI @jonrob

I just ran into a build error locally, and then noticed it is also present in the nightlies on master here and has been since Saturday morning.

I also noticed that nothing has been merged to Analysis or Phys (where the build seems to be looking when it fails) for awhile, so this must be an indirect result of something further upstream that was merged on Friday. I'm happy to help fix it but not sure where it's come from - any ideas @jonrob?