Prevent PyXML from importing, causing crashes

http://seclists.org/nmap-dev/2014/q2/318

Essentially, we import the xml name, then override its search path,
stripping out the _xmlplus paths that PyXML uses. This leaves only the
Python 2 standard library path, which is what Zenmap was written for.

ndiff/ndiff.py

@@ -18,6 +18,11 @@ import difflib
 import getopt
 import sys
 import time
+
+# Prevent loading PyXML
+import xml
+xml.__path__ = [x for x in xml.__path__ if "_xmlplus" not in x]
+
 import xml.sax
 import xml.sax.saxutils
 import xml.dom.minidom