The route under test does `send_error "Error $x", "5$x";` with `$x=42`. The Error object has a default title of 'Error 542' (from the status), but the actual error message is 'Error 42'.

Both strings are present in the HTML rendered output and the default hashref that is serialized from the Error object, so its not really necessary to change that test, but the test note indicated that its a test for the error message, so I modified that regex.