Add missing import

dmlib/utils/webutils.py

@@ -24,6 +24,7 @@
 from twisted.web import client, error, http
 from twisted.internet import protocol, reactor, defer, task
 from twisted.python import failure
+from twisted.python.compat import nativeString, intToBytes, unicode, itervalues
 from urlparse import urlunparse
 from urllib import splithost, splittype
 import gzip