http: try to read existing data in buffer under EVHTTP_CON_READ_ON_WRITE_ERROR There are two possible ways of getting response from the server: - processing existing bufferevent buffer - reading from the socket (even after write() errored with -1, it is still possible) But we did not tried the first option, only the second one. Fixes: http/read_on_write_error (on freebsd/osx)