This fetcher is to be used with PyPi mirrors exposing the "legacy" API, such as devpi.
A variant of this fetcher has been used in poetry2nix for years and
has served us well there to support private PyPi mirrors and Devpi.
Example usage:
``` nix
fetchPypiLegacy {
file = "urllib3-1.26.2.tar.gz";
hash = "sha256:19188f96923873c92ccb987120ec4acaa12f0461fa9ce5d3d0772bc965a39e08";
pname = "urllib3";
url = "https://pypi.org/simple";
}
```
cc @lewo who wrote the this originally
cc contributors @rskew @gmacon @jperras @Smaug123
