This is useful because the Error enum in its ApiError error variant exports that type, so in order to match on the error value it's necessary to use the same version of `nix` as this crate uses.

The idiom in this case is to reexport `nix` (or reexporting `Errno` would likely be fine as well, but I'm not sure if `nix` leaks in other ways maybe so I propose exporting the entire `nix` to be sure that it's correct.)