def validate_system(system):
    """
    Ensure build system has the requisite fields.
    """
    required = {'requires', 'build-backend'}
    if not (required <= set(system)):
        message = "Missing required fields: {missing}".format(
            missing=required-set(system),
        )
        raise ValueError(message)

    Ensure build system has the requisite fields.
    
product/gradle-plugin/src/main/python/pip/_vendor/pep517/build.py