def test_nullbooleanfield_blank(self):
        """
        Regression test for #13071: NullBooleanField should not throw
        a validation error when given a value of None.

        """
        nullboolean = NullBooleanModel(nbfield=None)
        try:
            nullboolean.full_clean()
        except __HOLE__ as e:
            self.fail("NullBooleanField failed validation with value of None: %s" % e.messages)
dataset/ETHPy150Open AppScale/appscale/AppServer/lib/django-1.5/tests/regressiontests/model_fields/tests.py/BasicFieldTests.test_nullbooleanfield_blank