I'm on OS X 10.9.5 (I know) and attempting to install any package using the nightly version (cargo 1.31.0-nightly (ad6e5c003 2018-09-28)) results in: ``` $ cargo install cargo-cov Updating crates.io index error: [48] An unknown option was passed in to libcurl ``` Adding `-v` doesn't reveal the source of error. `curl crates.io` with or without https works. Stable cargo 1.29.0 (524a578d7 2018-08-05) and cargo 1.30.0-beta (05e9b01fc 2018-09-21) work fine. I first suspected network censorship was the reason and tried to configure a proxy in ~/.cargo/config, but that didn't have any effect. I'm not an active rust user, so I'm not sure if/how I can troubleshoot this further without delving in too deep.