[Nix-dev] Haskell-env (via nix-shell) - am I doing this right?

[Peter Simons]

Hi Matthias,

 > error: cannot delete path
 > ‘/nix/store/pqj35vwax89ljdhcca02a330ii4zzhiw-haskell-clientsession-0.9.1.1.drv’
 > since it is still alive

https://github.com/NixOS/nixpkgs/issues/7792#issuecomment-100882553
discusses this problem. You have packages in one of your profiles that
depend on haskell-clientsession, so it can't be removed.

I hope this helps,
Peter