First discovered in these logs, it looks like Cargo isn't correctly detecting a spurious network failure:
error: failed to download from `https://crates.io/api/v1/crates/docopt/1.0.2/download`
Caused by:
[92] Stream error in the HTTP/2 framing layer (HTTP/2 stream 11 was not closed cleanly: INTERNAL_ERROR (err 2))
That's one that Cargo should automatically restart and attempt to redownload!