title: Heroku Rails asset pipeline fails to precompile after adding font
body: <p>I'm trying to add a font to my Rails app this is what I've done:</p>
  
  <p>Added fonts to:</p>
  
  <pre><code>-app
  --assets
  ---fonts
  </code></pre>
  
  <p>SCSS:</p>
  
  <pre><code>@font-face {
    font-family: LigatureSymbols;
  
    src: font-url('LigatureSymbols211.eot');
    src: local('LigatureSymbols'),
         font-url('LigatureSymbols211.eot?#iefix') format('embedded-opentype'),
         font-url('LigatureSymbols211.woff') format('woff'),
         font-url('LigatureSymbols211.ttf') format('truetype'),
         font-url('LigatureSymbols211.svg#LigatureSymbols') format('svg');
  
    font-weight: normal;
    font-style: normal;
  }
  </code></pre>
  
  <p><code>production.rb</code>:</p>
  
  <pre><code>config.assets.paths &lt;&lt; Rails.root.join('app', 'assets', 'fonts')
  config.assets.precompile += %w( .svg .eot .woff .ttf )
  </code></pre>
  
  <p>But when I push to my Heroku production server I get this:</p>
  
  <pre><code>-----&gt; Preparing app for Rails asset pipeline
         Running: rake assets:precompile
         I, [2013-05-06T06:21:07.804043 #2036]  INFO -- : Writing /tmp/build_2snusxy9gm4d7/public/assets/LigatureSymbols211-c5b7db18fa0fcd910e92fee751776047.eot
         I, [2013-05-06T06:21:07.809822 #2036]  INFO -- : Writing /tmp/build_2snusxy9gm4d7/public/assets/LigatureSymbols211-09ff8be41a6bee98c834e9a278bb8b28.otf
         I, [2013-05-06T06:21:07.812685 #2036]  INFO -- : Writing /tmp/build_2snusxy9gm4d7/public/assets/LigatureSymbols211-1f682b1be252dbf6182d606a185b603f.svg
         I, [2013-05-06T06:21:07.819262 #2036]  INFO -- : Writing /tmp/build_2snusxy9gm4d7/public/assets/LigatureSymbols211-9e88765b872185b22e519da056cba9f0.ttf
         I, [2013-05-06T06:21:07.829518 #2036]  INFO -- : Writing /tmp/build_2snusxy9gm4d7/public/assets/LigatureSymbols211-a2d90ca6deff46bfcf9cade63d4902ce.woff
         I, [2013-05-06T06:21:07.838351 #2036]  INFO -- : Writing /tmp/build_2snusxy9gm4d7/public/assets/rails-5f9b3f343d9831cbf50b9bc980faf39b.png
         I, [2013-05-06T06:21:17.072501 #2036]  INFO -- : Writing /tmp/build_2snusxy9gm4d7/public/assets/application-6af5b81b9fcc820f1d43b4135f00317e.js
         rake aborted!
         undefined method `[]' for nil:NilClass
         (in /tmp/build_2snusxy9gm4d7/app/assets/stylesheets/application.css)
  </code></pre>
  
  <p>I tried to add a <code>required</code> line in my <code>application.css</code> but that wouldn't work either.</p>
  
  <p><strong>EDIT:</strong></p>
  
  <p>I can access <code>localhost:5000/assets/LigatureSymbols-2.11.eot</code> on my dev machine when running the server.  Not sure if this might help narrow what's going wrong</p>
  
  <p><strong>EDIT 2:</strong></p>
  
  <p>The code works with the SCSS font commented out, is there a syntax error?</p>
  
  <p><strong>EDIT 3:</strong></p>
  
  <p>This is at the top of the trace stack:</p>
  
  <pre><code>.../sprockets-2.9.2/lib/sprockets/sass_functions.rb:63:in `sprockets_context'
  .../sprockets-2.9.2/lib/sprockets/sass_functions.rb:42:in `font_url'
  </code></pre>
  
  <p>is there something wrong with my <code>font-url</code> calls?</p>
  
  <p><strong>EDIT 4:</strong></p>
  
  <p>Removed dashes from font filenames and changed scss to reflect, but same error persists</p>
  
  <p><strong>EDIT 5:</strong></p>
  
  <p>Generated CSS on local machine:</p>
  
  <pre><code>@font-face {
    font-family: LigatureSymbols;
    src: font-url("LigatureSymbols211.eot");
    src: local("LigatureSymbols"), font-url("LigatureSymbols211.eot?#iefix") format("embedded-opentype"), font-url("LigatureSymbols211.woff") format("woff"), font-url("LigatureSymbols211.ttf") format("truetype"), font-url("LigatureSymbols211.svg#LigatureSymbols") format("svg");
    font-weight: normal;
    font-style: normal; }
  </code></pre>