Add gerrit retries for HTTP 409 Conflict responses.

BUG=crbug.com/854886,b/110032771
R=tandrii@google.com

Change-Id: Iabd67f8042ab3bc7c6ef15101effeeebf39d4500
Reviewed-on: https://chromium-review.googlesource.com/1111007Reviewed-by: Andrii Shyshkalov <tandrii@chromium.org>
Commit-Queue: Michael Moss <mmoss@chromium.org>

gerrit_util.py

@@ -393,9 +393,9 @@ def ReadHttpResponse(conn, accept_statuses=frozenset([200])):
       raise GerritAuthenticationError(response.status, reason)
 
     # If response.status < 500 then the result is final; break retry loop.
-    # If the response is 404, it might be because of replication lag, so
+    # If the response is 404/409, it might be because of replication lag, so
     # keep trying anyway.
-    if ((response.status < 500 and response.status != 404)
+    if ((response.status < 500 and response.status not in [404, 409])
         or response.status in accept_statuses):
       LOGGER.debug('got response %d for %s %s', response.status,
                    conn.req_params['method'], conn.req_params['uri'])

recipes/trigger_recipe_roller.txt

@@ -6,7 +6,8 @@ All they had was one poor machine under a desk, and its name was Batty,
 the Build and Test Yeti.
 
 As the CI needs of the browser grew, Batty, the Build and Test Yeti, got
-a new friend:
+a new friend, but this information was marked RVG, so it was months before
+any details were revealed.
 
 
 The End!