example failure: https://evergreen.mongodb.com/task_log_raw/mongo_rust_driver_tests__async_runtime~async_std_auth_and_tls~auth_and_tls_os~ubuntu_20.04_test_4.4_sharded_cluster_patch_5a0192cf1ba11d9e44c453e14f90d32231689166_6160a067850e613cedf3b697_21_10_08_19_47_52/0?type=T#L1228