I updated my Rails test app from 4.1 to 4.2. However when I pushed to OpenShift I got the following error
You have already activated rack 1.5.2, but your Gemfile requires rack 1.6.0.
Using bundle exec may solve this. (Gem::LoadError)
I found the answer on Google Groups here. The root cause is that OpenShift is dependent on Rack 1.5.2 and Passenger 4.0.18. The proper fix will have to wait until they update their versions of that software. Until then to fix this error, ssh into the OpenShift app and in the app-root folder run
gem install rack
→ posted on June 15, 2015development