create a script which can audit the /etc/apt/preference.d and /etc/apt/source.d folder to ensure only managed resources exist. Once complete we should be able to add
resource {'apt::pin': purge => true } resource {'apt::source': purge => true }
or more likley
class {'apt': purge_sources =>true}
we should be able to do this comparing /var/lib/puppet/state/last_run_report.yaml with the relevent folders