flaky test now sees different error message

tls_settings_test.go

@@ -111,17 +111,19 @@ func TestBrokenTLS_ClientPlainText(t *testing.T) {
 	// client connection (usually) succeeds since client is not waiting for TLS handshake
 	e, err := createTestServerAndClient(serverCreds, nil)
 	if err != nil {
-		if strings.Contains(err.Error(), "deadline exceeded") {
-			// It is possible that connection never becomes healthy:
+		if strings.Contains(err.Error(), "deadline exceeded") ||
+			strings.Contains(err.Error(), "use of closed network connection") {
+			// It is possible that the connection never becomes healthy:
 			//   1) grpc connects successfully
 			//   2) grpc client tries to send HTTP/2 preface and settings frame
 			//   3) server, expecting handshake, closes the connection
 			//   4) in the client, the write fails, so the connection never
 			//      becomes ready
-			// More often than not, the connection becomes ready (presumably
-			// the write to the socket succeeds before the server closes the
-			// connection). But when it does not, it is possible to observe
-			// timeouts when setting up the connection.
+			// The client will attempt to reconnect on transient errors, so
+			// may eventually bump into the connect time limit. This used to
+			// result in a "deadline exceeded" error, but more recent versions
+			// of the grpc library report any underlying I/O error instead, so
+			// we also check for "use of closed network connection".
 			return
 		}
 		t.Fatalf("failed to setup server and client: %v", err)