Gem::RemoteFetcher#fetch_https

# File tmp/rubies/ruby-3.0.5/lib/rubygems/remote_fetcher.rb, line 207
def fetch_http(uri, last_modified = nil, head = false, depth = 0)
  fetch_type = head ? Net::HTTP::Head : Net::HTTP::Get
  response   = request uri, fetch_type, last_modified do |req|
    headers.each {|k,v| req.add_field(k,v) }
  end

  case response
  when Net::HTTPOK, Net::HTTPNotModified then
    response.uri = uri
    head ? response : response.body
  when Net::HTTPMovedPermanently, Net::HTTPFound, Net::HTTPSeeOther,
       Net::HTTPTemporaryRedirect then
    raise FetchError.new('too many redirects', uri) if depth > 10

    unless location = response['Location']
      raise FetchError.new("redirecting but no redirect location was given", uri)
    end
    location = Gem::Uri.new location

    if https?(uri) && !https?(location)
      raise FetchError.new("redirecting to non-https resource: #{location}", uri)
    end

    fetch_http(location, last_modified, head, depth + 1)
  else
    raise FetchError.new("bad response #{response.message} #{response.code}", uri)
  end
end