mandrill-api-ruby
It is a mirror for an official Mandrill API gem. For some reason the gem is currenly hosted at https://bitbucket.org/mailchimp/mandrill-api-ruby which is not so rubyist-friendly as github.
Unfortunately, the gem is no longer supported see: https://bitbucket.org/mailchimp/mandrill-api-ruby/pull-requests/8/fix-json-version/diff
Thank you for writing in, I apologize for the delay in getting back to you. Currently, we do not have any official support for those public libraries any longer. We are more than happy to pass along the feedback to our developers, but I can not make promises that there will be any updates. However, as the code is public, you are entirely welcome to manipulate and edit it as needed to work with newer version of Python. I understand that this is not the ideal situation, but I am not privy to any information of upcoming updates to our Ruby wrappers.
How To Use
All info you can find at the official RTFM page.
Credits
Send all your love to Mandrill API maintainers and commiters, not to me <3