node-gyp: gyp can't find Python, despite Python running when you type "python"

I’m trying to install windows-registry on Windows 10 with Node 8.2.1 and NPM 5.3.0, and when the ref dependency is hit, node-gyp kicks in. However, it seems to fail when it tries to run python, despite the fact that python has a PATH entry and will run perfectly fine both when just executing “python” on the command line, or when exec/spawning a command called “python”.

The error log is as follows:

c:\Users\Mike\Documents\git\temp\pluginboutique>npm install windows-registry

> ref@1.3.4 install c:\Users\Mike\Documents\git\temp\pluginboutique\node_modules\ref
> node-gyp rebuild


c:\Users\Mike\Documents\git\temp\pluginboutique\node_modules\ref>if not defined npm_config_node_gyp (node "C:\Program Files\nodejs\node_modules\npm\bin\node-gyp-bin\\..\..\node_modules\node-gyp\bin\node-gyp.js" rebuild )  else (node "" rebuild )
gyp ERR! configure error
gyp ERR! stack Error: Can't find Python executable "C:\Program Files\Python35\python.EXE", you can set the PYTHON env variable.
gyp ERR! stack     at PythonFinder.failNoPython (C:\Program Files\nodejs\node_modules\npm\node_modules\node-gyp\lib\configure.js:483:19)
gyp ERR! stack     at PythonFinder.<anonymous> (C:\Program Files\nodejs\node_modules\npm\node_modules\node-gyp\lib\configure.js:508:16)
gyp ERR! stack     at C:\Program Files\nodejs\node_modules\npm\node_modules\graceful-fs\polyfills.js:284:29
gyp ERR! stack     at FSReqWrap.oncomplete (fs.js:152:21)
gyp ERR! System Windows_NT 10.0.15063
gyp ERR! command "C:\\Program Files\\nodejs\\node.exe" "C:\\Program Files\\nodejs\\node_modules\\npm\\node_modules\\node-gyp\\bin\\node-gyp.js" "rebuild"
gyp ERR! cwd c:\Users\Mike\Documents\git\temp\pluginboutique\node_modules\ref
gyp ERR! node -v v8.2.1
gyp ERR! node-gyp -v v3.6.2
gyp ERR! not ok
npm WARN optional SKIPPING OPTIONAL DEPENDENCY: fsevents@1.1.2 (node_modules\fsevents):
npm WARN notsup SKIPPING OPTIONAL DEPENDENCY: Unsupported platform for fsevents@1.1.2: wanted {"os":"darwin","arch":"any"} (current: {"os":"win32","arch":"x64"})

npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! ref@1.3.4 install: `node-gyp rebuild`
npm ERR! Exit status 1
npm ERR!
npm ERR! Failed at the ref@1.3.4 install script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.

I don’t understand why there would be any reason to be looking for Python in the indicated locations when there is already a PATH binding that makes python run just fine:

c:\Users\Mike\Documents\git\temp\pluginboutique>python
Python 3.5.2 (v3.5.2:4def2a2901a5, Jun 25 2016, 22:18:55) [MSC v.1900 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>>

But even then, that is the correct location as is evidenced by:

c:\Users\Mike\Documents\git\temp\pluginboutique>"C:\Program Files\Python35\python.EXE"
Python 3.5.2 (v3.5.2:4def2a2901a5, Jun 25 2016, 22:18:55) [MSC v.1900 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>>

And even node will happily run “python” through exec/spawn:

c:\Users\Mike\Documents\git\temp\pluginboutique>node
> var spawn = require('child_process').spawn;
undefined
> var willError = spawn('obviousnonexistentcommand');
undefined
> Error: spawn obviousnonexistentcommand ENOENT
    at exports._errnoException (util.js:1024:11)
    at Process.ChildProcess._handle.onexit (internal/child_process.js:192:19)
    at onErrorNT (internal/child_process.js:374:16)
    at _combinedTickCallback (internal/process/next_tick.js:138:11)
    at process._tickDomainCallback (internal/process/next_tick.js:218:9)
> var python = spawn('python');
undefined
>