`brew install xz` before `make install_prereqs_homebrew` fixed this problem, so it's likely as simple as the `wget` and `libpng` issues. 'wget', by the way, is still not installed as part of the prere…
When cloning the repo as suggested:
git clone https://github.com/RobotLocomotion/drake-distro.git --recursive -b rigidbody
I got this error message (when cloning the spotless repo):
Cloning into …