[XML-SIG] Reconsidering NamespaceErr on '' and None

[Rich Salz]

I have an opensource SOAP toolkit that runs on several DOM's: PyXML 0.6,
the planned 0.7, and the FourThought 4dom and cDomlette.  I wrote my own
accessors, like this:
    _find_attr = lambda E, attr: \
        E.getAttributeNS(None, attr) or E.getAttributeNS("", attr)

This now breaks, raising 
  File "/usr/lib/python2.1/site-packages/_xmlplus/dom/NamedNodeMap.py",
line 81, in getNamedItemNS
    raise NamespaceErr("Use None instead of '' for empty namespace")

I think this is a mistake as it makes it difficult to write portable
code.

Instead, I think we should treat [NONE, '', xml.dom.EMPTY_NAMESPACE] as
equivalent for one release, and in 0.8 use an exception.

For now, I'm doing this:
	try:
		from xml.dom import EMPTY_NAMESPACE
		_find_attr = lambda E, attr: \
		    E.getAttributeNS(EMPTY_NAMESPACE, attr)
	except:
		# the definition from above


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