fix: roundup-demo, interactive mode would nuke an existing tracker. Tonu Mikk demonstrated a bug in roundup-demo. When invoked without a tracker home on the command line, it would nuke an existing directory specified interactively. There is still a minor bug. If an invalid home directory is specified, roundup-demo will prompt for the template to use before reporting: Error: Refusing to nuke non-tracker directory: but this doesn't cause data loss so not worth fixing at this time.

try:
    # Python 3+.
    from xmlrpc import client, server
    server.SimpleXMLRPCDispatcher
except (ImportError, AttributeError):
    # Python 2.
    import xmlrpclib as client  # noqa: F401
    import SimpleXMLRPCServer as server