For the fundraising Drupal instance, we have been relying on a Debian package of drush, the Drupal command-line tool. That package doesn't exist in Debian Buster.
We do have a repository in Gerrit for drush, but it hasn't been updated in years and is proving difficult to bring up to date with upstream.
Could you please reset wikimedia/fundraising/crm/drush to point to the latest commit in the 7.x branch of https://github.com/drush-ops/drush ? That sha1 is currently 22220827e48f774.
Drush now relies on composer to install dependencies. We need to check in everything to Gerrit since we can't run composer in our install process. Following our pattern with other repos, we would like a vendor submodule with its own repo at wikimedia/fundraising/crm/drush/vendor. Could you please create that for us (empty)?