Rails 3.1, Spree, and "rake aborted! Could not find a JavaScript runtime. See https://github.com/sstephenson/execjs for a list of available runtimes"

I keep getting the following error when trying to run Rails 3.1 with Spree commerce, right when running my first rake command 'rake db:create':
$ rake db:create

rake aborted!
Could not find a JavaScript runtime. See https://github.com/sstephenson/execjs for a list of available runtimes.


(See full trace by running task with --trace)

The solution is to manually add the following gems to your gem file (and run the obligatory 'bundle install' afterwards):
gem 'execjs'
gem 'therubyracer'

Hope that helps.