Although I agree that the Unicode Howto needs to provide enough information for someone to reason correctly about python3 unicode, I'd like to note that someone running into the encoding error on windows is *not* going to reach for the unicode howto to solve their problem.  Instead they will google the error message, and will find many helpful and unhelpful explanations and solutions.  But they currently won't find this document (at least not on the first page of results).

So, if you really want to help someone with this problem, you need to specifically include that error message in the text as example of a commonly encountered problem, and then give a directed solution.