Validate a pipeline configuration.

def validate_pipeline(conf, args):
    """Validate a pipeline configuration."""
    host = conf.config['instances'][args.host_instance]
    host_url = api.build_pipeline_url(build_instance_url(host))
    host_auth = tuple([conf.creds['instances'][args.host_instance]['user'],
                      conf.creds['instances'][args.host_instance]['pass']])
    verify_ssl = host.get('verify_ssl', True)
    validate_result = api.validate_pipeline(host_url, args.pipeline_id, host_auth, verify_ssl)
    return validate_result