title: Gem file with git remote failing on heroku push
body: <p>I have the following line in my gemfile:</p>
  
  <pre><code>gem 'client_side_validations', :git =&gt; "git@github.com:Dakuan/client_side_validations.git", :branch =&gt; "master", ref: '2245b4174ffd4b400d999cb5a2b6dccc0289eb67'
  </code></pre>
  
  <p>The repo it's pointing at is public and I can run bundle install / update locally just fine. When I try to push to Heroku I get the following error:</p>
  
  <blockquote>
  <pre><code>   Fetching git@github.com:Dakuan/client_side_validations.git
     Host key verification failed.
     fatal: The remote end hung up unexpectedly
     Git error: command `git clone 'git@github.com:Dakuan/client_side_validations.git' "/tmp/build_1xa9f06n4k1cu/vendor/bundle/ruby/1.9.1/cache/bundler/git/client_side_validations-56a04875baabb67b5f8c192c6c6743df476fd90f" --bare --no-hardlinks` in directory /tmp/build_1xa9f06n4k1cu has failed.
  </code></pre>
    
    <p>!
     !     Failed to install gems via Bundler.
     !
     !     Heroku push rejected, failed to compile Ruby/rails app</p>
  </blockquote>
  
  <p>Anyone got any ideas about what's going on here?</p>