metasploit-framework/lib/metasploit/framework/rails_version_constraint.rb

# Records the Bundler-style dependency constraint for the version of Rails to be
# used with the Metasploit Framework and Metasploit Pro.
module Metasploit
  module Framework
    module RailsVersionConstraint

      # The Metasploit ecosystem is not ready for Rails 4 as it uses features of
      # Rails 3.X that are removed in Rails 4.
      RAILS_VERSION = [ '>= 3.2.21', '< 4.0.0' ]
    end
  end
end