ams-lv2: use python3

[dotlambda]

It is python3-compatible since 1.1.5.

Motivation for this change

#18185

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nox --run "nox-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Determined the impact on package closure size (by running nix path-info -S before and after)
• Fits CONTRIBUTING.md.

---

cc @cillianderoiste
Note that this was not tested.

[GrahamcOfBorg]

Failure on aarch64-linux (full log)

Attempted: ams-lv2

Partial log (click to expand)

        {task 281473874608928: cxx analogmemory.cpp -> analogmemory.cpp.71.o}
['g++', '-I/build/source', '-DNDEBUG', '-fshow-column', '-DPLUGIN_CLASS=analogmemory', '-std=c++11', '-DURI_PREFIX="http://github.com/blablack/ams-lv2/"', '-DPLUGIN_URI_SUFFIX="analogmemory"', '-DPLUGIN_HEADER="src/analogmemory.hpp"', '-msse', '-mfpmath=sse', '-ffast-math', '-fPIC', '-I/build/source/build', '-I/build/source', '-I/build/source/build/src', '-I/build/source/src', '-I/nix/store/1qqd314dy5b0b38m2avwh9qvrq2kagia-lv2-1.14.0/include', '-I/nix/store/wlhl85s3inl15f832gvx3j2b1jm5mghc-lvtk-1.2.0/include/lvtk-1', '-I/build/source/build', '-DWAF_CXX_FEATURE_EXTENDED_INITIALIZER_LISTS=1', '-DHAVE_LV2=1', '-DHAVE_LVTK_PLUGIN=1', '../src/analogmemory.cpp', '-c', '-o', '/build/source/build/src/analogmemory.cpp.71.o']
 -> task in 'bitgrinder' failed (exit status 1):
        {task 281473874609208: cxx bitgrinder.cpp -> bitgrinder.cpp.72.o}
['g++', '-I/build/source', '-DNDEBUG', '-fshow-column', '-DPLUGIN_CLASS=bitgrinder', '-std=c++11', '-DURI_PREFIX="http://github.com/blablack/ams-lv2/"', '-DPLUGIN_URI_SUFFIX="bitgrinder"', '-DPLUGIN_HEADER="src/bitgrinder.hpp"', '-msse', '-mfpmath=sse', '-ffast-math', '-fPIC', '-I/build/source/build', '-I/build/source', '-I/build/source/build/src', '-I/build/source/src', '-I/nix/store/1qqd314dy5b0b38m2avwh9qvrq2kagia-lv2-1.14.0/include', '-I/nix/store/wlhl85s3inl15f832gvx3j2b1jm5mghc-lvtk-1.2.0/include/lvtk-1', '-I/build/source/build', '-DWAF_CXX_FEATURE_EXTENDED_INITIALIZER_LISTS=1', '-DHAVE_LV2=1', '-DHAVE_LVTK_PLUGIN=1', '../src/bitgrinder.cpp', '-c', '-o', '/build/source/build/src/bitgrinder.cpp.72.o']
 -> task in 'controltocv' failed (exit status 1):
        {task 281473874609488: cxx controltocv.cpp -> controltocv.cpp.73.o}
['g++', '-I/build/source', '-DNDEBUG', '-fshow-column', '-DPLUGIN_CLASS=controltocv', '-std=c++11', '-DURI_PREFIX="http://github.com/blablack/ams-lv2/"', '-DPLUGIN_URI_SUFFIX="controltocv"', '-DPLUGIN_HEADER="src/controltocv.hpp"', '-msse', '-mfpmath=sse', '-ffast-math', '-fPIC', '-I/build/source/build', '-I/build/source', '-I/build/source/build/src', '-I/build/source/src', '-I/nix/store/1qqd314dy5b0b38m2avwh9qvrq2kagia-lv2-1.14.0/include', '-I/nix/store/wlhl85s3inl15f832gvx3j2b1jm5mghc-lvtk-1.2.0/include/lvtk-1', '-I/build/source/build', '-DWAF_CXX_FEATURE_EXTENDED_INITIALIZER_LISTS=1', '-DHAVE_LV2=1', '-DHAVE_LVTK_PLUGIN=1', '../src/controltocv.cpp', '-c', '-o', '/build/source/build/src/controltocv.cpp.73.o']
builder for '/nix/store/4r3bai44m4n1kjhxy9qrbnj6y1bhfjk8-ams-lv2-1.2.1.drv' failed with exit code 1
error: build of '/nix/store/4r3bai44m4n1kjhxy9qrbnj6y1bhfjk8-ams-lv2-1.2.1.drv' failed

[GrahamcOfBorg]

Success on x86_64-linux (full log)

Attempted: ams-lv2

Partial log (click to expand)

shrinking /nix/store/ca1a26fsrwzvx4zmq3q6z9ajiaia8m70-ams-lv2-1.2.1/lib/lv2/ams.lv2/seq_8.so
shrinking /nix/store/ca1a26fsrwzvx4zmq3q6z9ajiaia8m70-ams-lv2-1.2.1/lib/lv2/ams.lv2/seq_12.so
shrinking /nix/store/ca1a26fsrwzvx4zmq3q6z9ajiaia8m70-ams-lv2-1.2.1/lib/lv2/ams.lv2/mixer_4ch.so
shrinking /nix/store/ca1a26fsrwzvx4zmq3q6z9ajiaia8m70-ams-lv2-1.2.1/lib/lv2/ams.lv2/lfo2_tempo_gui.so
shrinking /nix/store/ca1a26fsrwzvx4zmq3q6z9ajiaia8m70-ams-lv2-1.2.1/lib/lv2/ams.lv2/vcenvii.so
shrinking /nix/store/ca1a26fsrwzvx4zmq3q6z9ajiaia8m70-ams-lv2-1.2.1/lib/lv2/ams.lv2/lfo.so
strip is /nix/store/1hi76hr87bd1y1q1qjk0lv8nmcjip1c8-binutils-2.30/bin/strip
stripping (with command strip and flags -S) in /nix/store/ca1a26fsrwzvx4zmq3q6z9ajiaia8m70-ams-lv2-1.2.1/lib
patching script interpreter paths in /nix/store/ca1a26fsrwzvx4zmq3q6z9ajiaia8m70-ams-lv2-1.2.1
checking for references to /build in /nix/store/ca1a26fsrwzvx4zmq3q6z9ajiaia8m70-ams-lv2-1.2.1...

[dotlambda]

The failure on aarch64 was there before: https://hydra.nixos.org/job/nixpkgs/trunk/ams-lv2.aarch64-linux.

[infinisil]

Why not just change python -> python3? These lines looked better before.

[dotlambda]

Because absolute paths are always better.

[dotlambda]

Also, for example, someone might want to replace python3 by a different implementation like pypy, which does not provide the python executable afaik.

[infinisil]

Ah alright, the second reason is one I can live with :)