We've ran into the same problem: How to install ffi on Heroku
We've tracked it down to Compass trying to install an incompatible executable (FFI) on Heroku, and it's not installing. What's so silly about this is that we don't need FFI to install on Heroku, considering it's only a development mode dependency.
Compass needs to bundle it's dependencies in a way that doesn't install unnecessary gems/executables on a production server (use add_development_dependency
), or Heroku needs to allow it to install in the /tmp directory.
Unfortunately, we haven't solved this problem so we've reverted our code to not use the beta version of Compass and we're considering switching to Bourbon, which doesn't have unnecessary production dependencies.