Fix error if output directory didn't exist

Change-Id: Ib1fecac1433bf20d4c6c45a4f13b17ee8c864e73
diff --git a/subcommands/install.py b/subcommands/install.py
index a51461a..cc50b95 100644
--- a/subcommands/install.py
+++ b/subcommands/install.py
@@ -226,6 +226,10 @@
         update_repo {boolean} -- Whether to update the helm repositories locally
     """
     config = config_manager.get_config()
+
+    if not os.path.exists(output_dir):
+        os.mkdir(output_dir)
+
     _run_ytt(config, output_dir)
 
     namespace = config_manager.get_config()["namespace"]