If you have a rvmrc dotfile in your rails project and you are using an specific Gemset for your Ruby version, take care!!
Unicorn ALWAYS uses Ruby version @global gemset. You could get a template error like this: "Could not find XXXX in any of the sources"
If you want to fix quickly this issue you can copy your current gemset of files to global default gemset, like this example:
rvm gemset copy [email protected] 1.9.3@global