title: rake assets:precompile with sprockets on Heroku memory exceeded
body: <p>What seems to be running perfectly for me locally, and under 100MB of memory, seems an impossible task on the Dyno of a Heroku server...</p>
  
  <p>How can I find out what is causing this memory swalling in the task itself?</p>
  
  <pre><code>$heroku run bundle exec rake assets:precompile -a myapp            
  
  Running `rake assets:precompile` attached to terminal... 2014-09-21T22:35:19.129047+00:00 heroku[api]: Starting process with command `bundle exec rake assets:precompile` by example@domain.com
  up, run.3387
  2014-09-21T22:35:38.348540+00:00 heroku[run.3387]: Awaiting client
  2014-09-21T22:35:38.410272+00:00 heroku[run.3387]: Starting process with command `bundle exec rake assets:precompile`
  2014-09-21T22:35:38.489421+00:00 heroku[run.3387]: State changed from starting to up
  RSpec is not part of this bundle, skip specs.
  Warning. Error encountered while saving cache /app/.sass-cache/cce550dafbc86189868cd4c9d7eaf6d5c3eab036/application.sassc: can't dump anonymous class #&lt;Class:0x007f009904f9e8&gt;
  2014-09-21T22:36:04.665412+00:00 heroku[run.3387]: Process running mem=687M(134.3%)
  2014-09-21T22:36:04.665737+00:00 heroku[run.3387]: Error R14 (Memory quota exceeded)
  2014-09-21T22:36:24.743579+00:00 heroku[run.3387]: Process running mem=689M(134.7%)
  2014-09-21T22:36:24.743579+00:00 heroku[run.3387]: Error R14 (Memory quota exceeded)
  2014-09-21T22:36:44.586205+00:00 heroku[run.3387]: Process running mem=691M(135.0%)
  2014-09-21T22:36:44.586205+00:00 heroku[run.3387]: Error R14 (Memory quota exceeded)
  </code></pre>
  
  <p>"ls -la" seems to list the correct assets, that were compiled on deploy successfully. However when the app starts up, Sprockets fails to find the files contained in public/assets/*, Could it be a permissions error?</p>