Boost.python requires numpy. Fix function _run_python_script().

[wdobbe]

Specify library name and version: boost/all_versions

First fix:
Function _run_python_script was broken when provided script returns empty output.
And on Windows the script that _python_abiflags(self) sends to _run_python_script does return no output. As a result the _run_python_script returned something like

 ----Running------
> "python" -c "from __future__ import print_function; import sys; print(getattr(sys, 'abiflags', ''))"
-----------------

instead of an empty string. Result was the following error message when building the boost recipe with option without_python=False even though python libraries were present:

ERROR: boost/1.76.0: Invalid configuration: couldn't locate python libraries - make sure you have installed python development files

Second fix:
Build of Boost.python library will fail if python package numpy is not installed. Check for presence of numpy in validate().

---

• I've read the guidelines for contributing.
• I've followed the PEP8 style guides for Python code in the recipes.
• I've used the latest Conan client version.
• I've tried at least one configuration locally with the
  conan-center hook activated.

[CLAassistant]

All committers have signed the CLA.

[ghost]

I detected other pull requests that are modifying boost/all recipe:

• boost: Improve option for i18n backend #5553
• [boost] For Visual Studio, pass some values of settings.compiler.toolset to B2 #5119
• boost: header only boost::system #5051
• boost: use clang-win toolset when compiler=Visual Studio and compiler.toolset=ClangCL #4749
• Boost/1.72.0/mpi #3959

This message is automatically generated by https://github.com/ericLemanissier/conan-center-conflicting-prs so don't hesitate to report issues/improvements there.

[Nekto89]

Is numpy dependency new for Boost.Python? I'm currently using 1.74.0 that was built without conan and without numpy.

[wdobbe]

Is numpy dependency new for Boost.Python? I'm currently using 1.74.0 that was built without conan and without numpy.

From this vcpkg issue it seems that Boost should check during build if numpy is installed or not and decides whether to build boost numpy library based on that result. If it builds boost numpy this will result in an extra library (libboost_numpy39.lib on Windows).
So the question is why Boost starts to build the numpy library on my systems even when numpy package is not installed.

In general: if the check for python package numpy in this PR is a problem, then better to remove that part and think about how we can fix it properly later.

The other patch is more important, because it completely messes up the boost python build on Windows and it takes quite a bit of time and debugging to find out what is going wrong.

[wdobbe]

ps: I don't understand why the license/cla is shown as 'not signed yet'. I have already signed it multiple times and have submitted PRs before. I signed the CLA again yesterday, but no result yet.

[prince-chrismc]

The commits is @winfriedd ... you need to sign the CLA with that account

[wdobbe]

Thanks, I didn't even know I had that other Github account. I will close that asap.

[SSE4]

the following code could be used to detect numpy (better in another PR):

    @property
    def _has_numpy(self):
        return self._run_python_script("from __future__ import print_function; "
                                       "import numpy; "
                                       "print(numpy.__version__)")

[wdobbe]

Thanks. I noticed that when building the test_package with VS2019 linking the numpy.cpp executable fails with unresolved synbol errors to boost numpy. So I removed numpy stuff from this PR, needs more investigation.

[conan-center-bot]

All green in build 6 (4401448c02269adb572f88a52da804d707e1c1e2):

• boost/1.69.0@:
  All packages built successfully! (All logs)

• boost/1.70.0@:
  All packages built successfully! (All logs)

• boost/1.71.0@:
  All packages built successfully! (All logs)

• boost/1.72.0@:
  All packages built successfully! (All logs)

• boost/1.74.0@:
  All packages built successfully! (All logs)

• boost/1.73.0@:
  All packages built successfully! (All logs)

• boost/1.76.0@:
  All packages built successfully! (All logs)

• boost/1.75.0@:
  All packages built successfully! (All logs)

[uilianries]

LGTM