only include rubocop when we need it

moduleroot/Rakefile

@@ -1,12 +1,15 @@
 require 'puppetlabs_spec_helper/rake_tasks'
 require 'puppet_blacksmith/rake_tasks'
 require 'voxpupuli/release/rake_tasks'
-require 'rubocop/rake_task'
 require 'puppet-strings/rake_tasks'
 
-RuboCop::RakeTask.new(:rubocop) do |task|
-  # These make the rubocop experience maybe slightly less terrible
-  task.options = ['-D', '-S', '-E']
+if RUBY_VERSION >= '2.0.0'
+  require 'rubocop/rake_task'
+
+  RuboCop::RakeTask.new(:rubocop) do |task|
+    # These make the rubocop experience maybe slightly less terrible
+    task.options = ['-D', '-S', '-E']
+  end
 end
 
 PuppetLint.configuration.log_format = '%{path}:%{linenumber}:%{check}:%{KIND}:%{message}'