For the NEWS entry, I'd suggest putting "Library" for the category and use your commit message for the text at the end.

You should also fill out the CLA form posted in your PR by the bot. While we *can* overlook it for very simple changes, best to get it done anyway.

As to Jean-Marc's comment, what you are describing is basically a bug in a third-party library and should be reported to them. As far as I can tell, http.server handles the encoding just fine, and if the web package has overridden part of it then it needs to override the rest in order to send headers properly. We can be less surprising to subclasses by only sending str, but if they're handling the conversion to bytes we can't really help any more than that.