在Google Apps Marketplace中获取用户许可证-错误

Question

According to the new Google Apps Marketplace documentation , in order to get the status of a user license, it should be enough to make a simple GET request to https://www.googleapis.com/appsmarket/v2/userLicense/{applicationId}/{userId}?key={ApiKey} where applicationId is a number, userId an email and ApiKey a string taken directly from the Google Cloud Console under APIs -> {App name} -> Server Key -> Api Key .
I have also enabled the Google Apps Marketplace API in Google Cloud Console.

However, I always get the following error message:

{"error":
{"errors":[{"domain":"global","reason":"authError","message":"Invalid OAuth header","locationType":"header","location":"Authorization"}],
"code":401,"message":"Invalid OAuth header"}}

Can you help me?

EDIT: Following Arun Nagarajan's suggestion, I tried using a scope, but it still does not work. Here is my code (in Python on Google Appengine):

credentials = oauth2client.appengine.AppAssertionCredentials(scope='https://www.googleapis.com/auth/appsmarketplace.license')
http = credentials.authorize(http=httplib2.Http())
client = apiclient.discovery.build('appsmarket', 'v2', http=http, developerKey='XXXXXXXX')
entry = client.userLicense().get(applicationId='123456', userId='some_user@email.com').execute()

Answer 1

You have to use OAuth 2 with the https://www.googleapis.com/auth/appsmarketplace.license scope.

You cannot just get the license with just the server key.