In gRPC, individual RPCs end with a return status set by the server, which contains an error code and a message. There is currently no way to observe this status when using a gRPC stream via a DBClientSession. In fact, right now all RPCs created via DBClientSession are terminated by cancellation, which appears server side as a failure.

We should introduce a way to close a DBClientSession such that the termination status is preserved, and we should adopt that in the shell's exit path.