FWIW, I was getting this after updating Capistrano to > 2.14.0:
*** [err :: ourapp.net] cp: cannot stat `/home/deploy/www/ourapp/shared/assets/manifest.yml'
*** [err :: ourapp.net] : No such file or directory
I think symlinking the assets to the shared dir would fix it, but instead of messing around (gotta get this deploy out), I just downgraded cap back to 2.13.5.