nixos/test/fcitx5: add assertion message

[h7x4]

Followup for #346680

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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[h7x4]

@ofborg test fcitx5

[h7x4]

@ofborg test fcitx5

[h7x4]

@ofborg test fcitx5

[h7x4]

Would be real nice if this one could fail with the same assertion error that the previous PR failed with...

[h7x4]

@ofborg test fcitx5

[FliegendeWurst]

The test actually fails because fcitx_test.out doesn't exist. So this won't help to debug it.

[h7x4]

Are you sure? If fcitx_test.out did not exist, I would expect the test to fail at file_content = machine.succeed("cat ${user.home}/fcitx_test.out") instead of passing through and throwing the assertion error at the next line (https://github.com/NixOS/nixpkgs/runs/32108566210)

[FliegendeWurst]

Oh right. The particular run you linked is a timeout, but the other one does indeed hit the assertion.