If you have third party module that wants to use ElementTree (and XMLTreeBuilder by dependency) you can change ElementTree’s XMLTreeBuilder definition to the one provided by SimpleXMLTreeBuilder like so:
from xml.etree import ElementTree # part of python distribution
from elementtree import SimpleXMLTreeBuilder # part of your codebase
ElementTree.XMLTreeBuilder = SimpleXMLTreeBuilder.TreeBuilder
Now ElementTree will always use the SimpleXMLTreeBuilder whenever it’s called.
See also: http://groups.google.com/group/google-appengine/browse_thread/thread/b7399a91c9525c97