Not able to access pear.drush.org
The Pear installation method for Drush was deprecated many years ago; I am not sure how long it has been unavailable, but it will not be coming back. The recommended and supported ways to download Drush are:


Use composer
Clone the git repository, then run composer install
Download the .phar


The Drush Puppet module on drupal.org claims to support git and composer installation mechanisms; perhaps you'd have the best luck if you switched to using that one.