I'm under Linux, but get the following warning when compiling an extension module.  This only happens with 3.5+.

$ python setup.py build_ext --inplace 
running build_ext
building 'numba._helperlib' extension
C compiler: gcc -pthread -Wsign-compare -Wunreachable-code -DNDEBUG -g -fwrapv -O3 -Wall -Wstrict-prototypes -fPIC

compile options: '-I/home/antoine/35/lib/python3.5/site-packages/numpy/core/include -I/home/antoine/35/include/python3.5m -c'
Warning: Can't read registry to find the necessary compiler setting
Make sure that Python modules winreg, win32api or win32con are installed.
gcc: numba/_helpermod.c
[...]

This should be fixed in numpy.distutils. The warning exists in distutils.msvccompiler, which is deprecated and only remains in case people were importing it directly (the only reference in the stdlib is the test suite).

Do you have a reference or changeset to point to, so that the Numpy developers can understand easily what the issue is?

Issue #23970 added the new compiler class, but all that really changed is that the module name is now distutils._msvccompiler. You *still* shouldn't access it except through distutils.ccompiler.new_compiler(compiler='msvc'), which is how it always was.

I can't point to exactly where in numpy the issue is, but I'd guess it looks a lot like "import distutils.msvccompiler"

Distutils is now deprecated (see PEP 632) and all tagged issues are being closed. From now until removal, only release blocking issues will be considered for distutils.

If this issue does not relate to distutils, please remove the component and reopen it. If you believe it still requires a fix, most likely the issue should be re-reported at https://github.com/pypa/setuptools