Indeed, we did, thanks for letting me know my mistake :) I didn't get very far into making bytes literal disallow invalid sequences, as I ran into issues with _codecs.escape_decode throwing the warning even when the literal was fine, and I think I stopped there and figured I'd at least post that patch and see if people are interested in extending that modification to bytes (turns out so).

I forgot about docs, will do so soon, but I'll try to extend the patch for bytes first. I'll see if I can make literals warn but not e.g. _codecs.escape_decode (or anything else, really).

Thanks!