title: Heroku Deploy error: 'sh: Syntax error: EOF in backquote substitution' and undefined local variable or method `install_language_pack_gems'
body: <p>Heroku Deploy for Rails app is failing currently. I am getting the following error message. I haven't changed any gems or rails code but just changed some static HTML and CSS files.</p>
  
  <pre><code>-----&gt; Ruby app detected
  -----&gt; Compiling Ruby/Rails
  -----&gt; Using Ruby version: ruby-2.0.0
  -----&gt; Installing dependencies using 1.5.2
         Ruby version change detected. Clearing bundler cache.
         Old: ruby 2.0.0p247 (2013-06-27 revision 41674) [x86_64-linux]
         New: ruby 2.0.0p353 (2013-11-22 revision 43784) [x86_64-linux]
  sh: Syntax error: EOF in backquote substitution
  sh: Syntax error: EOF in backquote substitution
  /app/tmp/buildpacks/ruby/lib/language_pack/ruby.rb:760:in `block in purge_bundler_cache': undefined local variable or method `install_language_pack_gems' for #&lt;LanguagePack::Rails4:0x00000001974ab8&gt; (NameError)
  </code></pre>