If you’re installing twitter-bootstrap-rails 3.x on Rails 4.x.x and running into the following error:
‘twitter/bootstrap/bootstrap.less’ wasn’t found
First, remember that Rails 4.x has removed the :asset group from the Gemfile syntax, so if you’re using the group :assets, you can simply remove the gems from the assets group and it should work.
In my case, I initially loaded a new rails application with 4.0.x, then upgraded to 4.2.5, without also upgrading the sass-rails version from 4.0.2 to 5.0. If you’ve removed the gems from the assets group, still running into the same error above, and your situation is similar, then try updating your Gemfile’s sass-rails line to:
gem 'sass-rails', '~> 5.0'
bundle update sass-rails
to get the latest version.