4.3 Upgrade fails with foreign key constraint due to required financial_type_id column being added for tables that have rows

Currently we are trying to add financial_type_id column NOT NULL to civicrm_payment_processor table with FK to civicrm_financial_type.id. If the DB being upgraded has one or more existing rows in civicrm_payment_processor table - you will get this FATAL error:

ALTER TABLE `civicrm_payment_processor` ADD CONSTRAINT `FK_civicrm_payment_processor_financial_type_id` FOREIGN KEY (`financial_type_id`) REFERENCES `civicrm_financial_type` (`id`) [nativecode=1452 ** Cannot add or update a child row: a foreign key constraint fails (`civicrm_42`., CONSTRAINT `FK_civicrm_payment_processor_financial_type_id` FOREIGN KEY (`financial_type_id`) REFERENCES `civicrm_financial_typ)]
DebugInfo

The upgrade script needs to insert reasonable defaults for financial types to be used in payment_processor table as well as the other tables where financial_type_is column is being added. Then all can be set to NOT NULL via a second ALTER TABLE command.

I've temporarily fixed this by changing column definition for civicrm_payment_processor.financial_type_id to DEFAULT NULL.