This is [causing build errors on Travis](https://travis-ci.org/tlyu/tor/jobs/315398995), which picked up the newest cargo nightly a week ago. As pointed out by Sebastian, the error appears to be due to [cargo issue #4563](https://github.com/rust-lang/cargo/issues/4563), which completely removed the `[root]` section of Cargo.lock files. Often, historically, the `[root]` section was used with an arbitrary non-existent crate, before cargo workspaces were implemented. However, our Cargo.lock file contains not only a `[root]`, but one which points to a non-arbitrary crate, `tor_util`. IIUC, we'll just need to remove that section. (While we're at it, we may want to update to the newest libc dependency.) I think we'll need to backport this to 0.3.0.x, since no newer cargos will build something with a `[root]` section.