Make rake fail when auto-corrected

Author: Mike Kenyon

Rakefile

@@ -30,7 +30,7 @@ task default: default_tasks
 task :rubocop_autocorrect do
   require 'rubocop'
   cli = RuboCop::CLI.new
-  exit_code = cli.run(%w(--auto-correct))
+  exit_code = cli.run(%w(--auto-correct --fail-level autocorrect))
   exit(exit_code) if exit_code != 0
 end