tinyproxy: hardcode /usr/bin/tinyproxy path

[3nprob]

installed at same path on debian/redhat/fedora.

• follow-up to tinyproxy: cleanup config and script #596
• Tinyproxy #157
• Handle tinyproxy path changed since Fedora 30+ #155

[3nprob]

This could maybe be considered breaking: Users can currently inject their own proxy replacing tinyproxy by putting it in e.g. /usr/local/bin (which is typically writable from AppVM). Not sure if anyone legitimately relies on this or if it's just a potential injection point that's better closed off. I'd lean against the latter.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 71.10%. Comparing base (4c5c36e) to head (1dc30a1).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #598   +/-   ##
=======================================
  Coverage   71.10%   71.10%           
=======================================
  Files           3        3           
  Lines         481      481           
=======================================
  Hits          342      342           
  Misses        139      139           

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[marmarek]

Hmm, do you know what NixOS does? It surely doesn't have /usr/bin/tinyproxy... @CertainLach

[3nprob]

Is/would NixOS actually be using this implementation in the first place? This package has plenty of references to /usr/bin as it is.

[CertainLach]

Hmm, do you know what NixOS does? It surely doesn't have /usr/bin/tinyproxy... @CertainLach

Usually, everything needs to be patched for NixOS; Not many of Qubes packages even rely on PATH, and then there is lots of expectations regarding script locations

This won't make the current patchset any worse.
https://github.com/CertainLach/nixos-qubes/blob/trunk/pkgs/by-name/qu/qubes-core-agent-linux/package.nix#L97

Actually, for NixOS, I would even prefer absolute paths to PATH lookups, because it is much easier to debug. I have audit rules in place, where I can see when the package with lacking patches is trying to call something, and I can react to that.

Still this is annoying to fix/try to find a proper way to rewrite the path, and it would be better if everything was configurable in a single file, but it is easier than the implicit dependencies.