To address the issue you can install the most recent version of ruby as described by @Sash

\curl -sSL https://get.rvm.io | bash -s stable rvm install ruby-2.0.0-p451 ruby -v sudo gem install json 

To address the issue you can install the most recent version of ruby as described by @Sash. You can use the following commands to do so. In case you already have installed rvm, you don't need to reinstall it.

#Install rvm \curl -sSL https://get.rvm.io | bash -s stable   #Install ruby version 2.0.0-p451 rvm install ruby-2.0.0-p451 #Print ruby version to verify that it was installed successfully ruby -v #Install json gem sudo gem install json