powerdns-admin: fix build

[Flakebi]

Motivation for this change

Since the last python updates, powerdns-admin failed to build.

Fix the dnspython pin (it was updated) and pin jsonschema in bravado-core to fix the build.

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/)
• 22.05 Release Notes (or backporting 21.11 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
  • (Release notes changes) Ran nixos/doc/manual/md-to-db.sh to update generated release notes
• Fits CONTRIBUTING.md.

[zhaofengli]

Tested to work 🚀 I haven't got a chance to look at the breakage since the last update, thank you for getting that sorted out!

[jonringer]

Pinning within python-modules is highly discouraged. This will potentially introduce incompatible versions in a user's environment as either the new pinned version or the original version will be imported at runtime, breaking one of the packages.

The preference to handling this is to relax version bounds in the "install_requires" field. (could be in setup.py, pyproject.toml, requirements or others). In most cases, packages are still compatible with small API changes which may warrant a major version bump. We use test suites to verify that the package still works correctly.

If the package is still incompatible with the latest major version, then the most proper way to handle this is make an issue with the upstream package to adopt the latest major version. Or if upstream is not very responsive, you are free patch the source to make it compatible.

In very few circumstances, two versions of the same package are allowed to exist if the packages are extremely difficult to package. Some examples of this are tensorflow, which has huge ecosystems built around it and is hard to package. Another is django, which has 2 actively developed versions, and large ecosystems built around each.

One exception to this is applications, due to the way buildPythonApplication and toPythonApplication functions work, the related derivations will not bleed dependencies between packages. If the package doesn't need to be imported by other python modules, then this package would be a good candidate to convert into application. You can look at https://github.com/NixOS/nixpkgs/blob/master/pkgs/tools/admin/awscli/default.nix as an example of using an overlay within a python application.

Another valid exception is pinning within the same interpreter version. If a package no longer supports older-but-still-relevant interpreter versions, then you're free to pin a package for an interpreter. This was very common with python2, but less common amongst python3 interpreters. (e.g. if (pythonOlder "3.8" then <older pkg> else <latest package> ;)

Info on buildPythonApplication can be found here.
Info on toPythonApplication can be found here.

[Flakebi]

It looks like bravado-core does not work with jsonschema 4, there’s an upstream PR to pin it to <4 because of bugs: Yelp/bravado-core#385
As bravado-core is a library, I also don’t know a way to override it for all dependencies once, therefore the override of swagger-spec-validator to not end up with two different versions of jsonschema (which does not compile).

[Flakebi]

Powerdns-admin was fixed differently in #174329