Hey there, I'm trying out nix packager on a non-nixos distro. I have it installed and tried using a declarative file to list out packages I want installed per this release note in the manual https://nixos.org/nix/manual/#ssec-relnotes-1.6.0  Once I do that and run 
```
nix-env -f my-packages.nix -ir
```
The packages I listed in my file install, however nix-env returns "command not found" after doing so, and I have to re-install nix packager to get it to run....

My question is: Is this a bug or operator difficulty?