require railtie only if Rails::Railtie is defined
require railtie only if Rails::Railtie is defined

The constant Rails can occur in many other gems besides RoR itself, like rails-html-sanitizer and rails-dom-testing dependencies of actionview, which does not depend on RoR or Rails::Railtie. If it more reliable to test for the actual Rails::Railtie.
paulelliott/fabrication,paulelliott/fabrication