Change all Postgres foreign keys to on update cascade - generates sql which you can execute.

gen_sql_fk_to_cascade_option.sql

select
    cl2.relname as child_table,
    att2.attname as "child_column",
    cl.relname as "parent_table",
    att.attname as "parent_column",
    conname,
    'alter table ' || cl2.relname || ' drop constraint ' || conname || ';' as drop_stmt,
    'alter table ' || cl2.relname || ' add constraint ' || conname 
        || ' foreign key (' || att2.attname || ') references ' || cl.relname 
        || ' on update cascade deferrable initially deferred;' as create_stmt
from
   (select
        unnest(con1.conkey) as "parent",
        unnest(con1.confkey) as "child",
        con1.confrelid,
        con1.conrelid,
        con1.conname
    from
        pg_class cl
        join pg_namespace ns on cl.relnamespace = ns.oid
        join pg_constraint con1 on con1.conrelid = cl.oid
    where
        cl.relname not like 'django%' and cl.relname not like 'auth%'
        and ns.nspname = 'public'
        and con1.contype = 'f'
   ) con
   join pg_attribute att on
       att.attrelid = con.confrelid and att.attnum = con.child
   join pg_class cl on
       cl.oid = con.confrelid
   join pg_class cl2 on cl2.oid = con.conrelid
   join pg_attribute att2 on
       att2.attrelid = con.conrelid and att2.attnum = con.parent;