title: Rails not loading .less files with Twitter Bootstrap
body: <p>I've been running Twitter Bootstrap successfully for months on my Rails 3.2.1 app</p>
  
  <p>I did a push to Heroku and the push failed on assets:precompile and the whole app crashed</p>
  
  <p>Running assets:precompile locally also failed with the following error:</p>
  
  <pre><code>no such file to load -- less
  (in /blah/blah/app/assets/stylesheets/bootstrap_and_overrides.css.less)
  </code></pre>
  
  <p>There have been no changes to my bootstrap_and_overrides.css.less or bootstrap_defaults.css.less files, but I suspect there has been a Gem update (how can I tell?)</p>
  
  <p>I have managed partial recovery by ADDING the gems:</p>
  
  <pre><code>gem 'less-rails-bootstrap'
  gem 'therubyracer'
  </code></pre>
  
  <p>(rubyracer being required by the other gem)</p>
  
  <p>I also did a rails g bootstrap:install -f and reinstated any custom lines in bootstrap_and_overrides from a backup</p>
  
  <p>I also reverted to a Git commit from where I knew it was working</p>
  
  <p>However, I have only partial success - with some site CSS styling now different than originally</p>
  
  <p>What is it that has happened here? And how can I go back to my original setup?</p>