If you are running Yosemite on your Mac, use or have brew installed and have not used brew in a while you might find that it is broken. you might see something like this:

/usr/local/bin/brew: /usr/local/Library/brew.rb: /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/bin/ruby: bad interpreter: No such file or directory. 

There are a variety of posts with different fixes (which did not work for me) but this one worked perfectly. http://vancelucas.com/blog/fixing-homebrew-on-osx-yosemite-10-10/

It ended up being the simplest fix (no edits required) for me. I tried two others and had to back both out for various reasons.

What prompted me to use brew was that I am always interested in static sites and stumbled on Hugo at http://gohugo.io/ and wanted to give it a try. More to come on that.