Duck typing is great let's do more of it

Don't hardcode which exception is to be considered an HTTP error, instead
embrace the duck typing philosphy and make any exception that have a get_response
method an HTTP Exception.

The rational behind this, beside the obvious advantage of duck typing over hardcoded
exception and subclass check, is that we don't want to be stuck with using Werkzeug
exception classes, since this later is hard to extend !
That's not duck typing :) "If it looks like a duck and walks/quack/flies etc. like a duck, it is a duck"

If you check by class, than everyone has to subclass your class for them to work ! but sadly subclassing is not easy, specially if you have too many stuff in your parent class, where developers end up having to work around it to just have there subclass as they wish, beside not everything fit in inheritance !

And that's where duck typing come in ! which basically said instead of checking subclass I will check the interface, this philosophy fit very well with dynamic languages since you can monkey patch almost everything !