Here is my error:
rake aborted! Gem::LoadError: You have already activated rake 10.3.1, but your Gemfile requires rake 10.2.2. Prepending `bundle exec` to yo
I meet the similar problem. My solution is change the line of rake version "gem 'rake', '~> 10.3'" in file Gemfile, delete Gemfile.lock and run 'bundler install', the new Gemfile.lock will show the new version 10.3.1. Then everything will be fine.