Adds the values of the existing config to the config dictionary.

def append_existing_values(schema, config):
    """
    Adds the values of the existing config to the config dictionary.
    """

    for section_name in config:
        for option_name in config[section_name]:
            option_value = config[section_name][option_name]

            # Note that we must preserve existing values, wether or not they
            # exist in the schema file!
            schema.setdefault(section_name, {}).setdefault(option_name, {})['value'] = option_value

    return schema