I think we can also remove the `src/ext/rust/vendor/rand-8c5b0ac51d` manually vendored dependency (and if not, we can at least definitely remove `src/ext/rust/vendor/rand-8c5b0ac51d/master.zip`). This is currently [breaking Travis builds](https://travis-ci.org/torproject/tor/jobs/374671123), and doing this [fixes the builds](https://travis-ci.org/isislovecruft/tor/builds/375039767).