avoid unhandled promise rejection on wrongly initialized stub #494
Description
Reported as googleapis/google-cloud-node#2086:
We should avoid unhandled promise rejections. Right now each method holds a promise for the method of the grpc client instance; this should be avoided.
We should:
- catch the error on createStub and throw an error
- or probably we should avoid using promises at all, stub creation and authentication should be delayed and done for the first time a method is called