Defines WP_ENV if it is not already defined

lib/config.php

@@ -13,6 +13,10 @@ add_theme_support('jquery-cdn');            // Enable to load jQuery from the Go
  */
 define('GOOGLE_ANALYTICS_ID', ''); // UA-XXXXX-Y (Note: Universal Analytics only, not Classic Analytics)
 
+if (!defined('WP_ENV')) {
+  define('WP_ENV', 'development'); // scripts.php checks for values 'production' or 'development'
+}
+
 /**
  * .main classes
  */