Adds instruction to readme to retrieve root certs from Google. (#1225)

Author: gguuss

iot/api-client/mqtt_example/README.rst

@@ -4,6 +4,7 @@ Google Cloud IoT Core API Python Samples
 ===============================================================================
 
 This directory contains samples for Google Cloud IoT Core API. `Google Cloud IoT Core`_ allows developers to easily integrate Publish and Subscribe functionality with devices and programmatically manage device authorization.
+Before you run the sample, you must retrieve the Google root certificate. For example, `wget https://pki.goog/roots.pem` or `curl https://pki.goog/roots.pem > roots.pem`.
 The following example runs the sample using the project ID `blue-jet-123` and the device name `my-python-device`:
 
     python cloudiot_mqtt_example.py \
@@ -71,9 +72,9 @@ To run this sample:
                                     [--mqtt_bridge_hostname MQTT_BRIDGE_HOSTNAME]
                                     [--mqtt_bridge_port {8883,443}]
                                     [--jwt_expires_minutes JWT_EXPIRES_MINUTES]
-    
+
     Example Google Cloud IoT Core MQTT device connection code.
-    
+
     optional arguments:
       -h, --help            show this help message and exit
       --project_id PROJECT_ID
@@ -104,4 +105,5 @@ To run this sample:
 
 
 
+
 .. _Google Cloud SDK: https://cloud.google.com/sdk/

iot/api-client/mqtt_example/README.rst.in

@@ -9,6 +9,10 @@ product:
     Subscribe functionality with devices and programmatically manage device
     authorization.
 
+    Before you run the sample, you must retrieve the Google root certificate.
+    For example, `wget https://pki.goog/roots.pem` or
+    `curl https://pki.goog/roots.pem > roots.pem`.
+
     The following example runs the sample using the project ID `blue-jet-123`
     and the device name `my-python-device`: