An assertion can be triggered in _mongoc_cluster_auth_node when called from 
mongoc_cluster_fetch_stream_single (at line 2429) in case speculative SCRAM auth failed with a network error.

• mongoc_cluster_fetch_stream_single calls _mongoc_cluster_finish_speculative_auth
• it calls _mongoc_cluster_auth_scram_continue
• _mongoc_cluster_run_scram_command fails with a network error
• _handle_network_error calls mongoc_cluster_disconnect_node which resets scanner node stream.