async def METHOD_NAME(self):
    config = Configuration()
    # set not-existent proxy and catch an error to verify that
    # the client library (aiohttp) tried to use it.
    config.proxy = 'http://localhost:8080/proxy'
    async with petstore_api.ApiClient(config) as client:
        pet_api = petstore_api.PetApi(client)
        with self.assertRaisesRegex(petstore_api.rest.aiohttp.client_exceptions.ClientProxyConnectionError,
                                    'Cannot connect to host localhost:8080'):
            await pet_api.get_pet_by_id(self.pet.id)