You are trying to install the gems for your rails application in a new computer, or by using ruby 2.4 and you get the following error:
An error occurred while installing json (1.8.3), and Bundler cannot continue. Make sure that `gem install json -v '1.8.3'` succeeds before bundling.
Remove your old Gemfile.lock file and run bundle again. A newer version of json (ie 1.8.6) should be installed.