Upgrade to Satellite 6.9 fails at db:migrate stage with 'could not create unique index "index_lookup_values_on_lookup_key_id_and_match"' error

Issue

• Red Hat Satellite upgrade to 6.9 fails with the following error.

  # satellite-maintain upgrade run --target-version 6.9
  ..
  ..
  2021-05-11 15:50:15 [NOTICE] [configure] 1700 out of 2326 done.
  2021-05-11 15:51:17 [ERROR ] [configure] '/usr/sbin/foreman-rake db:migrate' returned 1 instead of one of [0]
  2021-05-11 15:51:17 [ERROR ] [configure] /Stage[main]/Foreman::Database/Foreman::Rake[db:migrate]/Exec[foreman-rake-db:migrate]/returns: change from 'notrun' to ['0'] failed: '/usr/sbin/foreman-rake db:migrate' returned 1 instead of one of [0]
  2021-05-11 15:52:14 [ERROR ] [configure] /Stage[main]/Foreman::Database/Foreman::Rake[db:migrate]/Exec[foreman-rake-db:migrate]: Failed to call refresh: '/usr/sbin/foreman-rake db:migrate' returned 1 instead of one of [0]
  2021-05-11 15:52:14 [ERROR ] [configure] /Stage[main]/Foreman::Database/Foreman::Rake[db:migrate]/Exec[foreman-rake-db:migrate]: '/usr/sbin/foreman-rake db:migrate' returned 1 instead of one of [0]
  2021-05-11 15:52:39 [NOTICE] [configure] 1800 out of 2326 done.
  ..
  2021-05-11 15:52:40 [NOTICE] [configure] 2200 out of 2326 done.
  2021-05-11 15:52:47 [NOTICE] [configure] 2300 out of 2326 done.
  2021-05-11 15:52:51 [NOTICE] [configure] System configuration has finished.