bug#80734: Don't tell users *they* gave an improper argument

Some websites just say "we're sorry that action cannot be completed at this time try again later." 


And some say "that  command can't be completed. The system said 502. That's all we know."

So I'd be happy with one of those answers that just says "XYZ... that's all we know."

Any other way of fixing it (the  message that is. I don't care about the underlying disk problem.) will require years of linguistic research.