Add reminder on MacOS Catalina
diff --git a/tensorflow/lite/micro/examples/hello_world/README.md b/tensorflow/lite/micro/examples/hello_world/README.md
index c23b355..3e429dc 100644
--- a/tensorflow/lite/micro/examples/hello_world/README.md
+++ b/tensorflow/lite/micro/examples/hello_world/README.md
@@ -454,7 +454,7 @@
- STM32F7 discovery kit board
- Mini-USB cable
-- ARM Mbed CLI ([installation instructions](https://os.mbed.com/docs/mbed-os/v5.12/tools/installation-and-setup.html))
+- ARM Mbed CLI ([installation instructions](https://os.mbed.com/docs/mbed-os/v5.12/tools/installation-and-setup.html). Check it out for MacOS Catalina - [mbed-cli is broken on MacOS Catalina #930](https://github.com/ARMmbed/mbed-cli/issues/930#issuecomment-660550734))
- Python 2.7 and pip
Since Mbed requires a special folder structure for projects, we'll first run a
