Let's see what you got in the output.
Could not find a JavaScript runtime. See https://github.com/sstephenson/execjs for a list of available runtimes.
Hmm, sounds interesting. Let's follow that link.
ExecJS supports these runtimes:
- therubyracer - Google V8 embedded within Ruby
- therubyrhino - Mozilla Rhino embedded within JRuby
- Node.js
- Apple JavaScriptCore - Included with Mac OS X
- Microsoft Windows Script Host (JScript)
I think you should install one of these.