Print a more useful error message if the user used 'sudo' instead of 'rvmsudo'.
When running Passenger Standalone as root, run the worker process either as the --user user (so that Nginx can always access the app directory) or as root (because that's apparently what the user wants). This prevents a problem such as described at https://groups.google.com/d/msg/phusion-passenger/Io9EKsICt_I/f4ZJhakjgiQJ