[Python] FindPython3 fails on Python 3.5 on Windows

[asfimport]

-- Could NOT find Backtrace (missing: Backtrace_LIBRARY Backtrace_INCLUDE_DIR)
-- Found PythonInterp: C:/Miniconda/python.exe (found version "3.7.4")
-- Found PythonLibs: C:/Miniconda/libs/Python37.lib
CMake Error at cmake_modules/FindNumPy.cmake:58 (message):
  NumPy import failure:

  Traceback (most recent call last):

    File "<string>", line 1, in <module>

  ModuleNotFoundError: No module named 'numpy'

Call Stack (most recent call first):
  cmake_modules/FindPython3Alt.cmake:31 (find_package)
  src/arrow/python/CMakeLists.txt:22 (find_package)


-- Configuring incomplete, errors occurred!
See also "C:/Users/wesmc/code/arrow/cpp/build/CMakeFiles/CMakeOutput.log".
See also "C:/Users/wesmc/code/arrow/cpp/build/CMakeFiles/CMakeError.log".

This appears to work in 0.16.0

Reporter: Wes McKinney / @wesm

Related issues:

• [Python] Add wheel build script and Crossbow configuration for Windows on Python 3.5 (is related to)

_{Note: This issue was originally created as ARROW-8067. Please see the migration documentation for further details.}

[asfimport]

Antoine Pitrou / @pitrou:
Looks like it's finding Python 3.7.4 instead. Is Python 3.5 first on your PATH?

[asfimport]

Antoine Pitrou / @pitrou:
Perhaps "where python3" can give a clue.

[asfimport]

Wes McKinney / @wesm:
It's being called in an active conda environment on Windows with Python 3.5. If no one else beats me to it, I can tinker a bit and see where the script is getting fouled up

[asfimport]

Krisztian Szucs / @kszucs:
I found another but related findpython issue python 3.8 https://github.com/apache/arrow/pull/6592/checks?check_run_id=503647257#step:5:347

[asfimport]

Krisztian Szucs / @kszucs:
It might be related to this backported cmake commit Kitware/CMake@4e6b14c
I'm updating the cmake feedstock to 3.16.5 conda-forge/cmake-feedstock#114

[asfimport]

Wes McKinney / @wesm:
I'll update my environment and try again

[asfimport]

Wes McKinney / @wesm:
With CMake 3.16.4 and a fresh unpolluted dev environment this works fine now for me