Python 3.6.9 compatibility PyImport_GetModule

Description

There is (only) one function that prevents KiCad from being built with Python 3.6.9. See https://forum.kicad.info/t/kicad-build-error-netlist/29597/12?u=ferdymercury for more info. Cmake, works fine, but I then get the error: error: ‘PyImport_GetModule’ was not declared in this scope

Steps to reproduce

1. Try to compile with Python 3.6.9
2. CMake works, Make fails, because PyImport_GetModule is new from Python 3.7

KiCad Version

Application: KiCad

Version: (5.99.0-10785-gef96374eec-dirty), debug build

Libraries:
	wxWidgets 3.0.4
	libcurl/7.58.0 NSS/3.35 zlib/1.2.11 libidn2/2.0.4 libpsl/0.19.1 (+libidn2/2.0.4) nghttp2/1.30.0 librtmp/2.3

Platform: Linux 5.4.0-73-generic x86_64, 64 bit, Little endian, wxGTK, mate, x11

Build Info:
	Date: Jun  3 2021 13:30:24
	wxWidgets: 3.0.4 (wchar_t,wx containers,compatible with 2.8) GTK+ 3.22
	Boost: 1.65.1
	OCE: 6.9.1
	Curl: 7.58.0
	ngspice: 30
	Compiler: GCC 8.4.0 with C++ ABI 1013

Build settings:
	KICAD_USE_OCE=ON
	KICAD_SPICE=ON
	KICAD_STDLIB_DEBUG=OFF
	KICAD_STDLIB_LIGHT_DEBUG=OFF
	KICAD_SANITIZE_ADDRESS=OFF
	KICAD_SANITIZE_THREADS=OFF