Discovers schema file locations and relations.

    :param schema_dir: the directory schema files live inside
    :type schema_dir: string
    :param resource_listing: A swagger resource listing
    :type  resource_listing: dict
    :returns: a mapping from resource name to file path
    :rtype: dict

def build_schema_mapping(schema_dir, resource_listing):
    """Discovers schema file locations and relations.

    :param schema_dir: the directory schema files live inside
    :type schema_dir: string
    :param resource_listing: A swagger resource listing
    :type  resource_listing: dict
    :returns: a mapping from resource name to file path
    :rtype: dict
    """
    def resource_name_to_filepath(name):
        return os.path.join(schema_dir, '{0}.json'.format(name))

    return dict(
        (resource, resource_name_to_filepath(resource))
        for resource in find_resource_names(resource_listing)
    )