Provides a `select` function that picks the most appropriate `.whl` file
based on platform, arch, python version and manylinux/OSX - version.
- Adds unit tests for pep425
- Adds test for manylinux support
- Fixes overrides: `passhtru` must be extended, not overwritten
- Don't strip python packages: this screws up manylinux binaries
This adds the following new tests:
- trivial: minimaltest case
- override-support: verify overriding
- common-pkgs-1/2: verify commonly downloaded pypi pkgs can be built
Also adds some overrides as needed by some of the
tested packages.
We already have the name of the file that we need, so let's fetch it
directly instead of breaking it apart first, passing it to the Nixpkgs
fetchPypi, which would then put it together again.