Run a development server.

def devserver(arguments):
    """Run a development server."""
    import coil.web
    if coil.web.app:
        port = int(arguments['--port'])
        url = 'http://localhost:{0}/'.format(port)
        coil.web.configure_url(url)
        coil.web.app.config['DEBUG'] = True

        if arguments['--browser']:
            webbrowser.open(url)

        coil.web.app.logger.info("Coil CMS running @ {0}".format(url))
        coil.web.app.run('localhost', port, debug=True)
        return 0
    else:
        print("FATAL: no conf.py found")
        return 255