Attempting to build demo results in Fatal error

[jxc876]

I tried to build the demo:

$ npm install
...
$ grunt serve
Running "karma:continuous" (karma) task

Running "ngAnnotate:main" (ngAnnotate) task
>> 1 file successfully generated.

Running "uglify:build" (uglify) task
>> 1 file created.

Running "build:gh-pages" (build) task
Fatal error: spawn ENOENT

OS: Windows 7, 64 bit