'Raise because the same target was listed twice.'

def testMatchBuildContextError(self):

    context = '\nTest1    Context:\n        Client.labels:    [Test1]\n        ClientBuilder.target_platforms:\n                -    linux_amd64_deb\n                -    linux_i386_deb\n                -    linux_amd64_deb\n                -    windows_amd64_exe\n'
    conf = config.CONFIG.MakeNewConfig()
    conf.DEFINE_context('Test1    Context')
    conf.Initialize(parser=config_lib.YamlParser, data=context)
    conf.AddContext('Test1    Context')
    with self.assertRaises(type_info.TypeValueError):
        conf.MatchBuildContext('linux', 'amd64', 'deb')
