How to create a Watch face for Sense 2

[UrsusVanDraco]

I want to create a Watchface on my own.

My problem is: I don't get the environment running. the "Get me Started Guide" on the developer starting page might show a clue, but I walk through the guide point by point and I crash at  the step "Create a new project"

All I get are some error messages from the nvm that starts the following

Creating a new Fitbit SDK app in [enter Path here]

Installing packages. This might take a couple of minutes.
Installing @Fitbit/sdk and @Fitbit/sdk-cli...

npm ERR! code 1
npm ERR! path C:\Users\Ursus\Documents\GitHub\Fitbit-Isac\my-first-clock\node_modules\keytar
npm ERR! command failed
npm ERR! command C:\WINDOWS\system32\cmd.exe /d /s /c prebuild-install || node-gyp rebuild
npm ERR! gyp ERR! find Python
npm ERR! gyp ERR! find Python Python is not set from command line or npm configuration
npm ERR! gyp ERR! find Python Python is not set from environment variable PYTHON

Could please someone tell me, what I am doing wron (besides the audicity of using windows)

[Gondwana]

What version of node are you using?