[Satellite 6.1] katello installer returns "422 Unprocessable Entity" after upgrading from Satellite 6.0

Issue

After updating system packages with # yum update -y, it is not possible to successfully finish # katello-installer --upgrade. Following error messages are displayed during the upgrade process:

Upgrade Step: Running installer...
 qpid-config --ssl-certificate /etc/pki/katello/certs/java-client.crt --ssl-key /etc/pki/katello/private/java-client.key -b 'amqps://satellite.example.com:5671' add exchange topic event --durable returned 1 instead of one of [0]
 /Stage[main]/Certs::Candlepin/Exec[create candlepin qpid exchange]/returns: change from notrun to 0 failed: qpid-config --ssl-certificate /etc/pki/katello/certs/java-client.crt --ssl-key /etc/pki/katello/private/java-client.key -b 'amqps://satellite.example.com:5671' add exchange topic event --durable returned 1 instead of one of [0]
 /Stage[main]/Foreman_proxy::Register/Foreman_smartproxy[satellite.example.com]: Failed to call refresh: 422 Unprocessable Entity
 /Stage[main]/Foreman_proxy::Register/Foreman_smartproxy[satellite.example.com]: 422 Unprocessable Entity
Installing             Done                                               [100%] [...............................................................................................................................]
  Something went wrong! Check the log for ERROR-level output
  The full log is at /var/log/katello-installer/katello-installer.log