3scale system database backup using system-postgresql

Issue

It says in the documentation that a command must be executed to do backup, however, when executing them I get the error shown below:

$ oc rsh $(oc get pods -l 'deploymentConfig=system-mysql' -o json | jq -r '.items[0].metadata.name') bash -c 'export MYSQL_PWD=${MYSQL_ROOT_PASSWORD}; mysqldump --single-transaction -hsystem-mysql -uroot system' | gzip > system-mysql-backup.gz
Error from server (NotFound): pods "null" not found