I would like to use the python keyring package within my offlineimap configuration. I've added an overlay  
```
offlineimap = super.offlineimap.overrideAttrs (oldAttrs: {
    propagatedBuildInputs = with super.pythonPackages; oldAttrs.propagatedBuildInputs ++ [ keyring ];
  });
``` so that the wrapped offlineimap binary gets access to the keyring module but it doesn't seem to be picked up by nix-env -i offlineimap ?