Cannot upgrade using non-root installer if /tmp/couchbase-server-backup-config already exists

When attempting to upgrade Couchbase using the non-root installer on a system that went  over the such an upgrade before, when the /tmp/couchbase-server-backup-config directory was already created and not removed, the installer will fail, as can be seen below:

./cb-non-root-installer --upgrade --install-location /home/couchbase --package /tmp/couchbase-server-enterprise-6.6.0-centos7.x86_64.rpm 

2020/12/02T03:03:39 ERROR: Cannot create the directory /tmp/couchbase-server-backup-config to backup the config: [Errno 17] File exists: '/tmp/couchbase-server-backup-config'

This will require to firstly remove this directory before attempting the upgrade.

As this is a temporary directory, it should be removed post a successful upgrade.

This may also be relevant to previous versions.