有三件事造成了503错误.

There were three things that were creating the 503 error.

首先，我需要制作方法或整个Api

Firstly, I needed to make the method or entire Api require an Api Key. In this case I just applied it to the entire Api:

@endpoints.api(name='practice', version='v1', api_key_required=True)
class PracticeApi(remote.Service):

第二，在云控制台中生成Api密钥后，我需要在部署密钥之前，将密钥放入openapi.json文件.

Secondly, after I generated the Api Key in the cloud console I needed to put the Key into the openapi.json file before deploying it.

最后，我仍然收到验证错误:

Lastly, I was still getting a validation error:

ValidationError: Expected type <type 'unicode'> for field content, found (u'My Api Key', Variant(STRING, 9)) (type <type 'tuple'>)

get_unrecocoizedized_field_info()函数返回(值的元组，变体).响应未预期有元组，因此我将方法更新为仅显示值:

The get_unrecognized_field_info() function returns a tuple of (value, variant). A tuple was not expected by the response so I updated the method to only show value:

    def test_api_key(self, request):
        return TestResponse(content=request.get_unrecognized_field_info('key')[0])