python3.pkgs.jsonschema: add pip test dependency

[tjni]

Description of changes

This is needed but hidden by the fact that right now the Python setup hooks add pip to the environment.

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandbox = true set in nix.conf? (See Nix manual)
• 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/)
• 23.11 Release Notes (or backporting 23.05 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.

[FRidh]

Won't this cause a collision as it is now?

[tjni]

Won't this cause a collision as it is now?

I am honestly not sure why there isn't one. I echoed $PYTHONPATH and ran

${python.interpreter} -c "import sys;print(sys.path)"

in the preCheck phase, and neither showed pip more than once. The package still seems to build too. With that said, I also don't mind sitting on this until we can push everything together.