docs: Change error parsing to check for 'message' (#1083)

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Fixes #1082 🦕
diff --git a/docs/start.md b/docs/start.md
index ceac5dd..5efdcad 100644
--- a/docs/start.md
+++ b/docs/start.md
@@ -94,7 +94,10 @@
 Creating a request does not actually call the API. To execute the request and get a response, call the `execute()` function:
 
 ```python
-response = request.execute()
+try:
+    response = request.execute()
+except HttpError as e:
+    print('Error response status code : {0}, reason : {1}'.format(e.resp.status, e.error_details))
 ```
 
 Alternatively, you can combine previous steps on a single line: