def validate_not_in(needle,haystack, message='', exception=None):
    if needle in haystack:
        name,l = scoped_validation()
        ArgCheck(name,exception).validation(False,message,l)
Taken from regressiontests/syndication/tests.py.
dataset/ETHPy150Open ooici/pyon/pyon/util/arg_check.py/validate_not_in--crossover with--dataset/ETHPy150Open AppScale/appscale/AppServer/lib/django-1.4/django/contrib/gis/tests/geoapp/test_feeds.py/GeoFeedTest.assertChildNodes