Cannot fetch cargoDeps according to README

[oxalica]

I'm on current nixpkgs master.
Command: nix-prefetch cargo-flamegraph.cargoDeps --fetcher '<nixpkgs/pkgs/build-support/rust/fetchcargo.nix>'
Outputs:

warning: unknown setting 'experimental-features'
warning: unknown setting 'flake-registry'
warning: unknown setting 'experimental-features'
warning: unknown setting 'flake-registry'
error: attribute 'override' missing, at /nix/store/0x8sqpcg4kcpvw5nqabd8vhmn93da1f2-nix-prefetch-0.3.1/lib/nix-prefetch/fetcher.nix:37:65

[msteen]

To address this I would have to dig into a lot of details, so I will postpone it and address it in the cleanup/rewrite of nix-prefetch I am working on.