google impersonated service account: fail when scope not provided

[guillaumeblaquiere]

The scope is a requirement of the Service Account Credential generateAccessToken API

WIth "impersonated_service_account" credential type, if the scope is not set, the token request fail.

The idea is to add a scope by default (i.e. the Cloud Platform scope) if no scope is provided.

[liufuyang]

Took me a long time to figure out it is this issue by just looking at errors like this:

oauth2/google: status code 400: {
  "error": {
    "code": 400,
    "message": "Request contains an invalid argument.",
    "status": "INVALID_ARGUMENT"
  }
}

Will this be solved soon? Thanks @guillaumeblaquiere