Simplify the mkdir

lib/ansible/runner.rb

@@ -9,7 +9,7 @@ def run(env_vars, extra_vars, playbook_path)
 
       def run_via_cli(env_vars, extra_vars, playbook_path)
         Dir.mktmpdir("ansible-runner") do |base_dir|
-          mkdir(base_dir + '/project') # without this, there is a silent fail of the ansible-runner command see https://github.com/ansible/ansible-runner/issues/88
+          Dir.mkdir(File.join(base_dir, 'project')) # without this, there is a silent fail of the ansible-runner command see https://github.com/ansible/ansible-runner/issues/88
 
           result = AwesomeSpawn.run!(ansible_command(base_dir), :env => env_vars, :params => [{:cmdline => "--extra-vars '#{JSON.dump(extra_vars)}'", :playbook => playbook_path}])
 
@@ -21,10 +21,6 @@ def return_code(base_dir)
         File.read(File.join(base_dir, "artifacts/result/rc"))
       end
 
-      def mkdir(base_dir)
-        Dir.mkdir(base_dir) unless Dir.exist?(base_dir)
-      end
-
       def ansible_command(base_dir)
         # TODO add possibility to use custom path, e.g. from virtualenv
         "ansible-runner run #{base_dir} --json -i result"