I'm not against the considerations of the article regarding the user and its state of mind, but please do add as much technical detail as possible!
Even if an error message is a cryptic error code, that's better than a "Something went wrong" message. This is not better, or even friendlier, UX. An error code can be referenced, can be searched on the internet, can be passed around on a ticket or on a call... add parameters to your error template, reference the name of the file, the item name that does not respond, the HTTP error code... just give the user some transparency, some agency. Help the client build up a mental model of the error: when / how / why might it be happening.