caused the drive letter to cause urlopen() to think it was an unrecognized
URL scheme. This only passes system ids to urlopen() if the file does not
exist. It works on Windows & Unix.
It should work everywhere else as well.
xml.sax: Fix parse and parseString not to rely on ExpatParser
Greatly simplify import logic by using __import__
saxutils: Support Unicode strings and files as parameters to
prepare_input_source
