Thanks, @gerhard. Apparently I installed node some other way. Figuring out whether and when to install stuff via apt vs npm seems frought.
Egads. I think I installed node.js this weekend for some other reason some other way, so now I have npm@2.15.9 installed in /usr/bin and npm@3.3.6 in ~/.nvm/versions/node/v5.0.0/bin/npm.
Personal problems aside, @techAPJ, neither the Ubuntu Development Guide nor install-rails/linux mentions svgo. Perhaps you could update one of those?