[XML-SIG] Specializing DOM exceptions

[Martin v. Loewis]

>   I like this idea; very Pythonic!  The exceptions and .code values
> could live in xml/dom/__init__.py (or at least be imported there so
> the values are used from xml.dom, instead of from individual DOM
> implementations.

Good, I'll add this to PyXML first, and then move it over to Python
later. Please note that DOMException is already defined in
xml.dom(.__init__) of PyXML, so it is merely a matter of adding the
derived classes, and adding them in 4DOM.

>   I'd also like to see the .nodeType values defined this way, and
>   shared by the implementations.

It's more difficult with those, since the spec says they are defined
inside of the Node interface. We could deviate from the DOM spec in
this respect; clearly, they are located in the DOM interface to
facilitate the Java mapping (which also puts the ExceptionCodes inside
org.w3c.dom.DOMException).

Regards,
Martin