title: python argparse - add action to subparser with no arguments?
body: <p>I am adding subparsers to my parser to simulate subcommands functionality (for example code see: <a href="https://stackoverflow.com/questions/25332925/simple-command-line-application-in-python-parse-user-input/25368374#25368374">Simple command line application in python - parse user input?</a>). Now I want to add a <code>quit</code> subparser/command that takes no arguments and has a "quit" action attached. Is it possible ? How can I go about it ?</p>