message: Error out instead of asserting if TF fails to create a new session
diff: @@ -287,8 +287,9 @@ Status SingleMachine::ResetSession() {
  Env::Default(), SanitizeThreadSuffix("single_machine"), 2));
  session_.reset(NewSession(options_));
  - CHECK(session_ != nullptr);
  -
  + if (!session_) {
  + return errors::Unknown("Failed to create session");
  + }
  coordinator_.reset(new Coordinator());
  return Status::OK();
  