Build relies on OS install of python and fails if it's not there

[pieper]

This issue is broken out from #1281

@thewtex this is where the build fails because it cannot find python.

I agree with your comment that it would make sense for ITK-Wasm to use pixi for all python steps in order to have some control over versioning.

The issue is in dcmqi, so @fedorov may also need to be involved.

? Pixi task (configure-native-dicom in native): cmake -B$ITK_WASM_NATIVE_WORKSPACE/dicom-build -Spackages/dicom -GNinja
  -DITK_DIR:PATH=$ITK_WASM_ITK_BUILD_DIR
  -DBUILD_TESTING:BOOL=ON
  -DCMAKE_CXX_STANDARD:STRING=20
  -DCMAKE_BUILD_TYPE:STRING=Debug: (Configure dicom native binaries)
-- The C compiler identification is GNU 12.4.0
-- The CXX compiler identification is GNU 12.4.0
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working C compiler: /home/exouser/ITK-Wasm/.pixi/envs/native/bin/x86_64-conda-linux-gnu-cc - skipped
-- Detecting C compile features
-- Detecting C compile features - done
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: /home/exouser/ITK-Wasm/.pixi/envs/native/bin/x86_64-conda-linux-gnu-c++ - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Found OpenMP_C: -fopenmp (found version "4.5")
-- Found OpenMP_CXX: -fopenmp (found version "4.5")
-- Found OpenMP: TRUE (found version "4.5")
-- Setting C++ standard
-- Setting C++ standard - C++20
-- Configuring with build type 'Debug'
-- Checking if building as a Slicer extension
-- Checking if building as a Slicer extension - no (DCMQI_BUILD_SLICER_EXTENSION is OFF)
-- Checking if using built-in JsonCpp
-- Checking if using built-in JsonCpp - yes
CMake Warning (dev) at /home/exouser/ITK-Wasm/native/dicom-build/_deps/dcmqi_lib-src/CMakeLists.txt:251 (find_package):
  Policy CMP0148 is not set: The FindPythonInterp and FindPythonLibs modules
  are removed.  Run "cmake --help-policy CMP0148" for policy details.  Use
  the cmake_policy command to set the policy and suppress this warning.

This warning is for project developers.  Use -Wno-dev to suppress it.

CMake Error at /home/exouser/ITK-Wasm/.pixi/envs/native/share/cmake-3.30/Modules/FindPackageHandleStandardArgs.cmake:233 (message):
  Could NOT find PythonInterp (missing: PYTHON_EXECUTABLE) (Required is at
  least version "2.7")
Call Stack (most recent call first):
  /home/exouser/ITK-Wasm/.pixi/envs/native/share/cmake-3.30/Modules/FindPackageHandleStandardArgs.cmake:603 (_FPHSA_FAILURE_MESSAGE)
  /home/exouser/ITK-Wasm/.pixi/envs/native/share/cmake-3.30/Modules/FindPythonInterp.cmake:182 (FIND_PACKAGE_HANDLE_STANDARD_ARGS)
  /home/exouser/ITK-Wasm/native/dicom-build/_deps/dcmqi_lib-src/CMakeLists.txt:251 (find_package)


-- Configuring incomplete, errors occurred!

[fedorov]

Did you try initializing PYTHON_EXECUTABLE? I don't have any other ideas how to try to fix this, unfortunately.

[pieper]

No, I didn't try anything. I'm not too familiar with pixi, but it's likely that it provides something that could be used as PYTHON_EXECUTABLE for use in this scenario. I guess it would need to be added to the cmake line of whatever part of ITK Wasm configures dcmqi. Probably @thewtex knows where that would go.

[fedorov]

@jadh4v I am not sure if you are still working on this project, but I want to make sure you have seen this.

[thewtex]

@pieper thanks!

Patch in #1290

@fedorov can you please take a look at the corresponding QIICR/dcmqi#511

[thewtex]

@pieper are any other system python dependencies observed on main?