docs: def finalize_env(env):
      """
      Produce a platform specific env for passing into subprocess.Popen
      family of external process calling methods, and the supplied env
      will be updated on top of it.  Returns a new env.
      """
  
      keys = _PLATFORM_ENV_KEYS.get(sys.platform, [])
      if 'PATH' not in keys:
          # this MUST be available due to Node.js (and others really)
          # needing something to look for binary locations when it shells
          # out to other binaries.
          keys.append('PATH')
      results = {
          key: os.environ.get(key, '') for key in keys
      }
      results.update(env)
      return results