Whenever I `make test` on macOS, I get this warning: ``` relaycell/circbw: [forking] Jun 12 16:40:58.870 [warn] connection_edge_process_relay_cell: Bug: Somehow I had a connection that matched a data cell with stream ID 0. (on Tor 0.3.4.2-alpha b13abcce480ed766) ``` We should look if there's anything to be fixed.