Fixes #37966 - Rescue Candlepin error during force registration

after deleting certs from host. In this situation
Katello tries to update the consumer it just deleted.

app/services/katello/registration_manager.rb

@@ -154,13 +154,18 @@ def unregister_host(host, options = {})
         end
       end
 
+      # rubocop:disable Metrics/MethodLength
       def register_host(host, consumer_params, content_view_environments, activation_keys = [])
         new_host = host.new_record?
         unless new_host
           host.save!
           # Keep the kickstart repository ID so the host's Medium isn't unset
           # Important for registering a host during provisioning
-          unregister_host(host, :unregistering => true, :keep_kickstart_repository => true)
+          begin
+            unregister_host(host, :unregistering => true, :keep_kickstart_repository => true)
+          rescue RestClient::Gone
+            Rails.logger.debug("Host %s has been removed in preparation for reregistration" % host&.name)
+          end
           host.reload
         end
 
@@ -194,6 +199,7 @@ def register_host(host, consumer_params, content_view_environments, activation_k
           finalize_registration(host)
         end
       end
+      # rubocop:enable Metrics/MethodLength
 
       def check_registration_services
         ping_results = {}

test/services/katello/registration_manager_test.rb

@@ -279,6 +279,16 @@ def test_registration_existing_host
         ::Katello::RegistrationManager.register_host(@host, rhsm_params, [@content_view_environment])
       end
 
+      def test_force_registration_existing_host
+        ::Host::Managed.any_instance.expects(:update_candlepin_associations).times(1)
+        ::Katello::RegistrationManager.expects(:unregister_host).raises(RestClient::Gone)
+        ::Katello::RegistrationManager.expects(:create_in_candlepin)
+        ::Katello::RegistrationManager.expects(:finalize_registration)
+        Rails.logger.expects(:debug).with("Host #{@host.name} has been removed in preparation for reregistration")
+        Rails.logger.expects(:debug).with("ContentFacet: Marking CVEs changed for host #{@host.name}").times(1)
+        ::Katello::RegistrationManager.register_host(@host, rhsm_params, [@content_view_environment])
+      end
+
       def test_unregister_host
         ::Host::Managed.any_instance.stubs(:update_candlepin_associations)
         @host = FactoryBot.create(:host, :with_content, :with_subscription, :content_view => @content_view,