title: assets:precompile tries to compile a sass partial when it shouldn't
body: <p>Any idea why Rails' assets:precompile would try to compile a sass partial _accounts.css.sass when it's not listed in my precompile list? </p>
  
  <p>application.rb</p>
  
  <pre><code>config.assets.enabled = true
  config.assets.initialize_on_precompile = true
  
  config.assets.precompile += ['*.js', 'controllers/*.js', 'controllers/admin/*.js', 'controllers/shared/*.js', '*.coffee', 'application.css.sass', '*.css', '*.png', '*.jpg', '*.scss.erb']
  </code></pre>
  
  <p>_accounts.css.sass is only included by application.css.sass which has:</p>
  
  <pre><code>@import "account"
  </code></pre>
  
  <p>The error is:</p>
  
  <pre><code>Undefined mixin 'column'. (in _account.css.sass)
  </code></pre>
  
  <p>...because it uses compass, but the application.css.sass imports compass before importing _accounts.css.sass, so the partial shouldn't need to import compass.</p>