Added explicit info on the value of EVENT_HUB_NAME

After seeing this issue in Answers (https://learn.microsoft.com/en-us/answers/questions/1184327/how-to-fix-azure-eventhub-exceptions-authenticatio?page=1&orderby=helpful) and having a customer hit the exact same error today, I felt like this would be a beneficial add for the docs.
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cc: @spelluru

Author: da5is

articles/event-hubs/event-hubs-python-get-started-send.md

@@ -106,6 +106,8 @@ In this section, create a Python script to send events to the event hub that you
     * `EVENT_HUB_CONNECTION_STR`
     * `EVENT_HUB_NAME`
 
+    Make sure 'EVENT_HUB_NAME' is the name of the Event Hub and not the Event Hub Namespace.  If this value is incorrect, you will receive the error code "CBS Token authentication failed."
+
     ```python
     import asyncio
 
@@ -366,4 +368,4 @@ If you don't see events in the receiver window or the code reports an error, try
 
 In this quickstart, you've sent and received events asynchronously. To learn how to send and receive events synchronously, go to the [GitHub sync_samples page](https://github.com/Azure/azure-sdk-for-python/tree/master/sdk/eventhub/azure-eventhub/samples/sync_samples).
 
-For all the samples (both synchronous and asynchronous) on GitHub, go to [Azure Event Hubs client library for Python samples](https://github.com/Azure/azure-sdk-for-python/tree/master/sdk/eventhub/azure-eventhub/samples).
+For all the samples (both synchronous and asynchronous) on GitHub, go to [Azure Event Hubs client library for Python samples](https://github.com/Azure/azure-sdk-for-python/tree/master/sdk/eventhub/azure-eventhub/samples).