Satellite upgrade failing with errors pointing to IPA enrolment

Issue

While upgrading Satellite 6, satellite-installer finishes with an error in /var/log/foreman-installer/satellite.log:

[DEBUG 2018-08-26 08:18:33 main] Exit with status code: 1 (signal was 1)
[ERROR 2018-08-26 08:18:33 main] Errors encountered during run:
[ERROR 2018-08-26 08:18:33 main]  satellite: The system does not seem to be IPA-enrolled at /usr/share/foreman-installer/modules/foreman/manifests/config.pp:75 on node satellite.example.com
[ERROR 2018-08-26 08:18:33 main] Upgrade failed during the installation phase. Fix the error and re-run the upgrade.