Upgrading Red Hat Satellite server fails with error Procedures::Installer::Upgrade: Could not get default values

Issue

• Upgrading Red Hat Satellite server from 6.7 to 6.8 fails with below error:

  Running Migration scripts to Satellite 6.8
  ================================================================================
  Setup repositories:
  \ Configuring repositories for 6.8                                    [OK]
  --------------------------------------------------------------------------------
  Unlock packages:                                                      [OK]
  --------------------------------------------------------------------------------
  Update package(s) :                                                   [OK]
  --------------------------------------------------------------------------------
  Procedures::Installer::Upgrade: Could not get default values, check log file at /var/log/foreman-installer/satellite.log for more information
                                        [FAIL]
  Failed executing LANG=en_US.utf-8 satellite-installer  --disable-system-checks, exit status 25
  --------------------------------------------------------------------------------
  Scenario [Migration scripts to Satellite 6.8] failed.
  The following steps ended up in failing state:
    [installer-upgrade]