title: undefined method `sass' for #<Rails::Application::Configuration on Heroku
body: <p>I've looked around a bit and didn't find similar errors reported.
  I don't recall having modified my <a href="https://gist.github.com/1284427" rel="noreferrer"><code>production.rb</code></a>. And for good measure, here's my <a href="https://gist.github.com/3c19d928a8d34d723fa4" rel="noreferrer"><code>application.rb</code></a> </p>
  
  <p>Here's the stack trace from Heroku.</p>
  
  <pre><code>$ heroku run rake db:migrate --remote staging --trace
  
  Running rake db:migrate --trace attached to terminal... up, run.2
  /app/vendor/bundle/ruby/1.9.1/gems/rack-1.3.4/lib/rack/backports/uri/common_192.rb:53:      warning: already initialized constant WFKV_
  rake aborted!
  
  undefined method `sass' for #&lt;Rails::Application::Configuration:0x000000047c6fb0&gt;
  /app/vendor/bundle/ruby/1.9.1/gems/railties-3.1.1/lib/rails/railtie/configuration.rb:78:in `method_missing'
  /app/config/application.rb:63:in `&lt;class:Application&gt;'
  /app/config/application.rb:18:in `&lt;module:Instantice&gt;'
  /app/config/application.rb:17:in `&lt;top (required)&gt;'
  /app/Rakefile:5:in `require'
  /app/Rakefile:5:in `&lt;top (required)&gt;'
  /app/vendor/bundle/ruby/1.9.1/gems/rake-0.9.2/lib/rake/rake_module.rb:25:in `load'
  /app/vendor/bundle/ruby/1.9.1/gems/rake-0.9.2/lib/rake/rake_module.rb:25:in `load_rakefile'
  /app/vendor/bundle/ruby/1.9.1/gems/rake-0.9.2/lib/rake/application.rb:495:in `raw_load_rakefile'
  /app/vendor/bundle/ruby/1.9.1/gems/rake-0.9.2/lib/rake/application.rb:78:in `block in load_rakefile'
  /app/vendor/bundle/ruby/1.9.1/gems/rake-0.9.2/lib/rake/application.rb:129:in `standard_exception_handling'
  /app/vendor/bundle/ruby/1.9.1/gems/rake-0.9.2/lib/rake/application.rb:77:in `load_rakefile'
  /app/vendor/bundle/ruby/1.9.1/gems/rake-0.9.2/lib/rake/application.rb:61:in `block in run'
  /app/vendor/bundle/ruby/1.9.1/gems/rake-0.9.2/lib/rake/application.rb:129:in `standard_exception_handling'
  /app/vendor/bundle/ruby/1.9.1/gems/rake-0.9.2/lib/rake/application.rb:59:in `run'
  /app/vendor/bundle/ruby/1.9.1/gems/rake-0.9.2/bin/rake:32:in `&lt;top (required)&gt;'
  /app/vendor/bundle/ruby/1.9.1/bin/rake:19:in `load'
  /app/vendor/bundle/ruby/1.9.1/bin/rake:19:in `&lt;main&gt;'
  </code></pre>
  
  <p>I initially thought this line in the <code>application.rb</code> could be causing this (although it never had before). </p>
  
  <pre><code>config.sass.preferred_syntax = :sass
  </code></pre>
  
  <p>Removing it was fruitless though.</p>