The error was caused by chronic gem (a whenever gem dependency): it was colliding with Ruby 2. You can solve it with a simple bundle update whenever chronic
and you'll get the latest, non-colliding version.
In the future, if you need a fix before a new version of Chronic is officially released, point your Gemfile
directly at the git repo:
gem 'chronic', :git => 'git@github.com:mojombo/chronic.git'
gem 'whenever'