tl;dr: Install ruby 2.4.1 for your work on the master branch.
Now that the fine branch has been created, we can start working on the next release, and upgrading our ruby is a "fine" thing to start with...
Up until now, we have been supporting ruby 2.2 and 2.3 but only testing 2.3 on travis and the bot using ruby 2.2 for syntax.
In the near future, we'll be supporting ruby 2.3 and 2.4 on master and dropping 2.2. Travis will be testing 2.4, while the bot will be updated to use ruby 2.3 for syntax.
Note, manageiq master already supports ruby 2.4 via this pull request, so now is the time to use 2.4 on master and get all of our libraries 2.4 compatible.
The timeline and work items remaining can be found here.
One work item above worth highlighting is we'll have to upgrade our webmock version for ruby 2.4 support. As far as I can tell, this will require us to rerecord some VCR cassettes in the main repo but also in the various provider repos using VCR.
Please review the work items above, add missing tasks, and reach out if you can work on any of them or offer other help. Let's discuss in the core gitter channel.