Fixed #19260 - Added a comment to tutorial 1.

Thanks terwey for the suggestion.

docs/intro/tutorial01.txt

@@ -666,6 +666,7 @@ Save these changes and start a new Python interactive shell by running
     >>> Poll.objects.get(pub_date__year=2012)
     <Poll: What's up?>
 
+    # Request an ID that doesn't exist, this will raise an exception.
     >>> Poll.objects.get(id=2)
     Traceback (most recent call last):
         ...