rails g scaffold Error

rails g scaffold

Error: root/.rbenv/versions/2.2.2/lib/ruby/gems/2.2.0/gems/bundler-1.9.8/lib/bundler/runtime.rb:34:in `block in setup': You have already activated spring 1.3.6, but your Gemfile requires spring 1.3.4. Prepending `bundle exec` to your command may solve this. (Gem::LoadError)

引用

Fix :
1. spring stop
2. bundle update

Or
http://yehudakatz.com/2011/05/30/gem-versioning-and-bundler-doing-it-right/

Reference:http://stackoverflow.com/questions/29203272/couldnt-run-migration-after-spring-update-in-rails