pyocd works fine when installed through nix-shell:
$ nix-shell -p pyocd --run "pyocd --version"
0.34.3
However, when installed through home-manager, it fails:
$ pyocd --version
[…]
pkg_resources.DistributionNotFound: The 'cffi' distribution was not found and is required by cmsis-pack-manager
In both cases I am using the nixpkgs-unstable channel. Any idea of what happens?