Motivation for this change

In trying to fix the darwin py27 build for this package, realized it was an upstream problem. Opened upstream issue https://github.com/atztogo/spglib/issues/78, turns out the problem was an incorrect assertion and darwin/py27 was the only combination where its assert() wasn't acting as a no-op, so tripping up on this problem.

pythonPackages.seekpath reverse-dependency seems broken, so nox-review doesn't quite build fully, but this doesn't break anything new. Tested on non-nixos linux x86_64 and macos 10.13.

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nix-review --run "nix-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Determined the impact on package closure size (by running nix path-info -S before and after)
• Assured whether relevant documentation is up to date
• Fits CONTRIBUTING.md.