Mark python3Packages.krb5 broken and fix requests-kerberos on Darwin

[de11n]

Description of changes

Python krb5 package doesn't build on Darwin. I spent some time trying to fix it, but it will require more time than I can offer right now. It's causing requests-kerberos to fail on Darwin which is widely used. This should be a suitable stop-gap until we can figure out how to make Python krb5 work on Darwin.

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandboxing enabled in nix.conf? (See Nix manual)
  • sandbox = relaxed
  • sandbox = true
• Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
  • made sure NixOS tests are linked to the relevant packages
• Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage
• Tested basic functionality of all binary files (usually in ./result/bin/)
• 24.11 Release Notes (or backporting 23.11 and 24.05 Release notes)
  • (Package updates) Added a release notes entry if the change is major or breaking
  • (Module updates) Added a release notes entry if the change is significant
  • (Module addition) Added a release notes entry if adding a new NixOS module
• Fits CONTRIBUTING.md.

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[Kumm-Kai]

Building requests-kerberos now works on aarch64-darwin.
The package where I've noticed the broken build openstack-client now also successfully builds again.
However, I don't authenticate to OpenStack using Kerberos, so I can't confirm if that still works.

Thanks for the quick fix ❤️