[Radiant] "Could not find a JavaScript runtime" deploying Radiant 1.0.0rc4 to Heroku

[Mick Hollins]

Hi,
I'm attempting to deploy Radiant 1.0.0rc4 to Heroku, but I get the
following error:

     Could not find a JavaScript runtime

The full log output is here:

   https://gist.github.com/1698750

Anyone seen this before? Any help would be greatly appreciated.

thanks,
mick