'Test that we can not modify constant values during runtime.'

def testConstants(self):

    conf = config_lib.GrrConfigManager()
    conf.DEFINE_constant_string('Section1.const', 'test', 'A    test    string.')
    self.assertEqual(conf['Section1.const'], 'test')
    data = '\n[Section1]\nconst    =    New    string\n'
    conf.Initialize(data=data)
    self.assertRaises(config_lib.ConstModificationError, conf.Set, 'Section1.const', 'New    string')
    self.assertRaises(config_lib.ConstModificationError, conf.SetRaw, 'Section1.const', 'New    string')
