Running the script in a debian8 docker container leads to:
E: Unable to locate package postgresql-9.3-postgis-2.1
E: Couldn't find any package by regex 'postgresql-9.3-postgis-2.1'
E: Unable to locate package postgresql-server-dev-9.3
E: Couldn't find any package by regex 'postgresql-server-dev-9.3'
Running the script in a debian8 docker container leads to: