Bem, obrigado pela sua ajuda, mas as linhas abaixo funcionaram para mim.
export DEBIAN_FRONTEND="noninteractive"
sudo debconf-set-selections <<< "mariadb-server mysql-server/root_password password $PASSWORD"
sudo debconf-set-selections <<< "mariadb-server mysql-server/root_password_again password $PASSWORD"
sudo apt-get install -y mariadb-server python-mysqldb