You can try a query like the following to determine which table has that unique constraint defined:
SELECT n.nspname as schema_name,
co.conrelid::regclass as table_name,
co.conname as constraint_name,
pg_catalog.pg_get_constraintdef(co.oid, true) as constraing_def
FROM pg_constraint co
INNER JOIN pg_catalog.pg_class cl ON cl.oid = co.conrelid
LEFT JOIN pg_catalog.pg_namespace n ON n.oid = cl.relnamespace
WHERE co.conname = 'pegasus_config_scanner_id_name_key'
AND co.contype = 'u'