'twitter/bootstrap/responsive.less' wasn't found
I inadvertently ended up updating twitter-bootstrap-rails to 3.2.0 when I didn't specify a specific version in my gemfile. The previous version was at 2.2.8, which I rolled back to and everything works just fine now. The new version is missing the responsive.less file.
The set up for version 3.2.0 of twitter-bootstrap-rails is different from version 2.2.8.If you want to use version 3.2.0 you must update the setup as well. To do so, run this command:
rails generate bootstrap:install less