Verify that one or more resources were downloaded successfully.

def verify(opts):
    """
    Verify that one or more resources were downloaded successfully.
    """
    resources = _load(opts.resources, opts.output_dir)
    if opts.all:
        opts.resource_names = ALL
    invalid = _invalid(resources, opts.resource_names)
    if not invalid:
        if not opts.quiet:
            print("All resources successfully downloaded")
        return 0
    else:
        if not opts.quiet:
            print("Invalid or missing resources: {}".format(', '.join(invalid)))
        return 1