When playing with page creation on a local wiki several of my attempts to triage pages displayed a browser alert

An error occurred while marking the page as reviewed: $1

If you open the browser console's Net tab, the actual API error is

"error": {
    "code": "appendnotsupported",
    "info": "Can't append to pages using content model flow-board",
    "*": "See http://localhost/wiki/api.php for API usage"
}

Disregarding the circumstances of the error, the PageTriage JS should always provide a parameter and never display $1. The error handler function should use data.error.info if it is set, otherwise the internalerror message.

(The error circumstance here is T85030.)