title: Less::ParseError: variable @fa-css-prefix is undefined
body: <p>trying to deploy my Rails app to heroku and I get this error:</p>
  
  <pre><code>Less::ParseError: variable @fa-css-prefix is undefined
  </code></pre>
  
  <p>here is my Gemfile:</p>
  
  <pre><code>source 'https://rubygems.org'
  
  # Bundle edge Rails instead: gem 'rails', github: 'rails/rails'
  gem 'rails', '4.1.7'
  # Use postgresql as the database for Active Record
  gem 'pg'
  # Use SCSS for stylesheets
  gem 'sass-rails', '~&gt; 4.0.3'
  # Use Uglifier as compressor for JavaScript assets
  gem 'uglifier', '&gt;= 1.3.0'
  # Use CoffeeScript for .js.coffee assets and views
  gem 'coffee-rails', '~&gt; 4.0.0'
  # See https://github.com/sstephenson/execjs#readme for more supported runtimes
  gem 'therubyracer',  platforms: :ruby
  
  gem 'httparty'
  
  gem 'sorcery'
  
  gem 'less'
  
  # Use jquery as the JavaScript library
  gem 'jquery-rails'
  # Turbolinks makes following links in your web application faster. Read more: https://github.com/rails/turbolinks
  gem 'turbolinks'
  # Build JSON APIs with ease. Read more: https://github.com/rails/jbuilder
  gem 'jbuilder', '~&gt; 2.0'
  # bundle exec rake doc:rails generates the API under doc/api.
  gem 'sdoc', '~&gt; 0.4.0',          group: :doc
  
  # Spring speeds up development by keeping your application running in the background. Read more: https://github.com/rails/spring
  gem 'spring',        group: :development
  
  # Use ActiveModel has_secure_password
  # gem 'bcrypt', '~&gt; 3.1.7'
  
  # Use unicorn as the app server
  # gem 'unicorn'
  
  # Use Capistrano for deployment
  # gem 'capistrano-rails', group: :development
  
  # Use debugger
  # gem 'debugger', group: [:development, :test]
  </code></pre>
  
  <p>I get the error when I try to push to Heroku</p>
  
  <p><strong>EDIT:</strong></p>
  
  <p>../less/font-awesome.less</p>
  
  <pre><code>/*!
   *  Font Awesome 4.1.0 by @davegandy - http://fontawesome.io - @fontawesome
   *  License - http://fontawesome.io/license (Font: SIL OFL 1.1, CSS: MIT License)
   */
  
  @import "variables.less";
  @import "mixins.less";
  @import "path.less";
  @import "core.less";
  @import "larger.less";
  @import "fixed-width.less";
  @import "list.less";
  @import "bordered-pulled.less";
  @import "spinning.less";
  @import "rotated-flipped.less";
  @import "stacked.less";
  @import "icons.less";
  </code></pre>
  
  <p>../less/variables.less</p>
  
  <pre><code>// Variables
  // --------------------------
  
  @fa-font-path:        "../fonts";
  //@fa-font-path:        "//netdna.bootstrapcdn.com/font-awesome/4.1.0/fonts"; // for referencing Bootstrap CDN font files directly
  @fa-css-prefix:       fa;
  @fa-version:          "4.1.0";
  @fa-border-color:     #eee;
  @fa-inverse:          #fff;
  @fa-li-width:         (30em / 14);
  ...
  ...
  </code></pre>