Otherwise references to the Python interpreter inside the set are wrong, as demonstrated by:
``` nix
with import <nixpkgs> { };
let
python' = python3.override {
packageOverrides = final: prev: { requests = prev.requests.overridePythonAttrs(old: { version = "1337"; }); };
};
in python'.pkgs.python.pkgs.requests
```
which returns the _non_ overriden requests.
And the same with `self`:
```
with import <nixpkgs> { };
let
python' = python3.override {
self = python';
packageOverrides = final: prev: { requests = prev.requests.overridePythonAttrs(old: { version = "1337"; }); };
};
in python'.pkgs.python.pkgs.requests
```
which returns the overriden requests.
This can manifest itself as file collisions when constructing environments or as subtly incorrect dependency graphs.
Man, copy&paste to five places is just great :-/
The referenced upstream patch should fix the compatibility,
but it won't apply cleanly to this version, so I dropped the test.
