qtgui build scripts require python 2

[drew-parsons]

• Avogadrolibs: 1.92.1

• Qt: 5.12.5 (Debian 5.12.5+dfsg-2)

• OS: Debian unstable

• Version Linux 5.3.7-1

• Compiler g++ 9.2.1-14

Build scripts for the qtgui component require Python 2, find_package(PythonInterp 2) in

• avogadro/qtgui/CMakeLists.txt
• tests/qtgui/CMakeLists.txt

Python 2 is deprecated, will be no longer supported from 1 Jan 2020, so needs to be replaced with Python 3.

More problematically for avogadrolibs, the python module is supposed to be built with cmake -DUSE_PYTHON=ON. But python/CMakeLists.txt does require Python 3: find_package(PythonInterp 3 REQUIRED)

So there is a contradiction in the build. python2 is found for qtgui, and those python2 values found for PythonInterp are reused for the python build, which consequently fails since it needs python3:

-- Found GLEW: /usr/include
-- Found PythonInterp: /usr/bin/python2 (found suitable version "2.7.17", minimum required is "2")
-- Found LIBARCHIVE: /usr/include
CMake Error at /usr/share/cmake-3.13/Modules/FindPackageHandleStandardArgs.cmake:137 (message):
  Could NOT find PythonInterp: Found unsuitable version "2.7.17", but
  required is at least "3" (found /usr/bin/python2)
Call Stack (most recent call first):
  /usr/share/cmake-3.13/Modules/FindPackageHandleStandardArgs.cmake:376 (_FPHSA_FAILURE_MESSAGE)
  /usr/share/cmake-3.13/Modules/FindPythonInterp.cmake:159 (FIND_PACKAGE_HANDLE_STANDARD_ARGS)
  python/CMakeLists.txt:1 (find_package)


-- Configuring incomplete, errors occurred!

The qtgui scripts need to be updated for Python3.

[welcome]

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[ghutchis]

Sorry, I'm just getting to this now, because we're aiming for a 1.94 release. This should be fixed by #462

[ghutchis]

I'm marking this closed - thanks for the detailed report.