ORA-00001: unique constraint (FOO.SYS_C003567231) violated
The constraint is system-generated, based on UNIQUE being specified in the DDL, so the name is unhelpful. With no other information, finding the affected table can be difficult. You can query for the table with the following SQL:
select constraint_name, table_name from user_constraints where constraint_name='SYS_C003567231
This is a handy query to know, so I'm noting it here for my future reference. It's also described in a number of other blogs like this one.