I am using MacPorts and never had trouble installing cmake with it. Maybe use that?
Try installing Sphinx 1.3.1 with Anaconda?
I took an odd path: I “lost” homebrew, as in
brew was no longer a valid command on my terminal. So I re-installed homebrew and ran
brew install cmake. This time, I got the following message:
cmake 3.13.4 is already installed and up-to-date. Ok, good enough. Not sure what happened.