Python with Protobuf flake error

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1

I’m not super sure what’s happening here. I thought it’d be a good idea to get going quickly with flakes for a throwaway python project, so I pulled something from dev-templates and tweaked it.

I ended up with this:

{
  description = "A Nix-flake-based Python development environment";

  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/release-22.11";
    flake-utils.url = "github:numtide/flake-utils";
    mach-nix.url = "github:/DavHau/mach-nix";
  };

  outputs =
    { self
    , nixpkgs
    , flake-utils
    , mach-nix
    }:

    flake-utils.lib.eachDefaultSystem (system:
    let
      # overlays = [
      #   (self: super: {
      #     python = super.python311;
      #   })
      # ];

      # pkgs = import nixpkgs { inherit overlays system; };
      pkgs = import nixpkgs { inherit system; };
    in
    {
      devShells.default = pkgs.mkShell {
        packages = with pkgs; [ python311 virtualenv protobuf ] ++
          (with pkgs.python311Packages; [ pip protobuf ]);

        shellHook = ''
          ${pkgs.python}/bin/python --version
        '';
      };
    });
}

which throws a relatively weird error.

error: builder for '/nix/store/8v2nc3j1z6m1k3fzw51nn8sxlmxjp0h0-python3.11-pyext-0.8.drv' failed with exit code 1;
       last 10 log lines:
       > Executing setuptoolsBuildPhase
       > Traceback (most recent call last):
       >   File "/private/tmp/nix-build-python3.11-pyext-0.8.drv-0/source/nix_run_setup", line 8, in <module>
       >     exec(compile(getattr(tokenize, 'open', open)(__file__).read().replace('\\r\\n', '\\n'), __file__, 'exec'))
       >   File "setup.py", line 6, in <module>
       >     import pyext
       >   File "/private/tmp/nix-build-python3.11-pyext-0.8.drv-0/source/pyext.py", line 118, in <module>
       >     oargspec = inspect.getargspec
       >                ^^^^^^^^^^^^^^^^^^
       > AttributeError: module 'inspect' has no attribute 'getargspec'. Did you mean: 'getargs'?
       For full logs, run 'nix log /nix/store/8v2nc3j1z6m1k3fzw51nn8sxlmxjp0h0-python3.11-pyext-0.8.drv'.
error: 1 dependencies of derivation '/nix/store/45hvqqc10rgqjyn716cpb23x3xf2qhq1-python3.11-protobuf-4.21.8.drv' failed to build
error: 1 dependencies of derivation '/nix/store/ixisv4p5j0yw8l9d8a372x7xg3gyic5q-nix-shell-env.drv' failed to build

Not sure how to even start debugging this.

Ticket for the same on Github: Tweaked Python file throws error · Issue #20 · the-nix-way/dev-templates · GitHub

2

What’s weird about it? Looks like a fairly normal Python error stack.

Seems to lead pretty directly to

Try sticking to 3.10.

3

It also looks like this problem led to pyext being removed from nixpkgs after the 22.11 branch-off:

If I’m reading those right, updating the flake to use a 23.05 nixpkgs input may also do the trick.

4

Why would installing packages using this particular package manager throw a python error? When installing python packages I rarely get python errors and those that I get are pretty obscure.

So I changed the line to read:

nixpkgs.url = "github:NixOS/nixpkgs/release-23.05";

Now I get an even weirder error:

error: Package ‘python-2.7.18.6’ in /nix/store/k6k1ydb9gpcznys4pybzifmy6wg7wfkl-source/pkgs/development/interpreters/python/cpython/2.7/default.nix:330 is marked as insecure, refusing to evaluate.


       Known issues:
        - Python 2.7 has reached its end of life after 2020-01-01. See https://www.python.org/doc/sunset-python-2/.

       You can install it anyway by allowing this package, using the
       following methods:

       a) To temporarily allow all insecure packages, you can use an environment
          variable for a single invocation of the nix tools:

            $ export NIXPKGS_ALLOW_INSECURE=1

        Note: For `nix shell`, `nix build`, `nix develop` or any other Nix 2.4+
        (Flake) command, `--impure` must be passed in order to read this
        environment variable.

       b) for `nixos-rebuild` you can add ‘python-2.7.18.6’ to
          `nixpkgs.config.permittedInsecurePackages` in the configuration.nix,
          like so:

            {
              nixpkgs.config.permittedInsecurePackages = [
                "python-2.7.18.6"
              ];
            }

       c) For `nix-env`, `nix-build`, `nix-shell` or any other Nix command you can add
          ‘python-2.7.18.6’ to `permittedInsecurePackages` in
          ~/.config/nixpkgs/config.nix, like so:

            {
              permittedInsecurePackages = [
                "python-2.7.18.6"
              ];
            }
(use '--show-trace' to show detailed location information)

I’m not sure how or why it is trying to install python2.7.

5

I got help. Wiping the overlay made ${pkgs.python}/bin/python --version refer to python2.7. Replacing python with python3 fixed it.