[Python-modules-team] Bug#1060772: Bug#1060772: python3-jupyterlab: Using node-corepack downloads yarnpkg from Internet

[Yadd]

Hi,

depending on the use of "jupyterlab build":
  - when used manually, may prefer to launch yarnpkg
  - when used under Debian build/test, may prefer to use
    pkgjs-install-minimal

So proposition:
  - drop the patch 0003-Use-system-provided-yarn.js.patch
  - build a custom yarn.js that calls yarnpks or pkg-install-minimal
    depending on an environment variable