In upgrading to 5.20+ an error occured while running the database Case upgrade scripts.
Deletion Error There is a Payment Processor associated with selected Payment Processor type, hence it can not be deleted.
CiviCRM_API3_Exception: "API error: Could not delete payment processor type"
#0 /dir/wp/wp-content/plugins/civicrm/civicrm/CRM/Upgrade/Incremental/php/FiveTwenty.php(370): civicrm_api3("CaseType", "create", (Array:9))
#1 /dir/wp/wp-content/plugins/civicrm/civicrm/CRM/Upgrade/Incremental/php/FiveTwenty.php(289): CRM_Upgrade_Incremental_php_FiveTwenty::_processCaseTypeLabelName(FALSE, "7")
#2 /dir/wp/wp-content/plugins/civicrm/civicrm/CRM/Upgrade/Incremental/php/FiveTwenty.php(265): CRM_Upgrade_Incremental_php_FiveTwenty::_changeCaseTypeLabelToName(FALSE)
#3 /dir/wp/wp-content/plugins/civicrm/civicrm/CRM/Queue/Task.php(88): CRM_Upgrade_Incremental_php_FiveTwenty::changeCaseTypeLabelToName(Object(CRM_Queue_TaskContext))
#4 /dir/wp/wp-content/plugins/civicrm/civicrm/CRM/Queue/Runner.php(217): CRM_Queue_Task->run(Object(CRM_Queue_TaskContext))
#5 /dir/wp/wp-content/plugins/civicrm/civicrm/CRM/Queue/Page/AJAX.php(52): CRM_Queue_Runner->runNext(TRUE)
#6 /dir/wp/wp-content/plugins/civicrm/civicrm/CRM/Queue/ErrorPolicy.php(106): CRM_Queue_Page_AJAX::{closure}()
#7 /dir/wp/wp-content/plugins/civicrm/civicrm/CRM/Queue/Page/AJAX.php(54): CRM_Queue_ErrorPolicy->call(Object(Closure))
#8 /dir/wp/wp-content/plugins/civicrm/civicrm/CRM/Core/Invoke.php(250): CRM_Queue_Page_AJAX::runNext()
#9 /dir/wp/wp-content/plugins/civicrm/civicrm/CRM/Core/Invoke.php(84): CRM_Core_Invoke::runItem((Array:13))
#10 /dir/wp/wp-content/plugins/civicrm/civicrm/CRM/Core/Invoke.php(52): CRM_Core_Invoke::_invoke((Array:5))
#11 /dir/wp/wp-content/plugins/civicrm/civicrm.php(1465): CRM_Core_Invoke::invoke((Array:5))
#12 /dir/wp/wp-includes/class-wp-hook.php(288): CiviCRM_For_WordPress->invoke("")
#13 /dir/wp/wp-includes/class-wp-hook.php(312): WP_Hook->apply_filters("", (Array:1))
#14 /dir/wp/wp-includes/plugin.php(478): WP_Hook->do_action((Array:1))
#15 /dir/wp/wp-admin/admin.php(254): do_action("toplevel_page_CiviCRM")
#16 {main}