Bug 1425571 - fixups for release notifications, r=aki

Sends 'in the candidates directory', 'pushed to cdntest', etc emails only when the underlying dummy tasks succeed, avoiding false messages when graphs are cancelled or the dummy job fails for infrastructure reasons.

Also sets the body of the email to be the same string as the subject, as we used to do, to avoid unnecessary information about the dummy task.

taskcluster/taskgraph/transforms/release_notifications.py

@@ -56,7 +56,9 @@ def add_notifications(config, jobs):
             )
             subject = notifications['subject'].format(**format_kwargs)
             message = notifications['message'].format(**format_kwargs)
-            routes = ['notify.email.{email_dest}.on-any']
+            # we only send these on succces to avoid messages like 'blah is in the
+            # candidates dir' when cancelling graphs, dummy job failure, etc
+            routes = ['notify.email.{email_dest}.on-success']
             # Don't need this any more
             del job['notifications']
         else:
@@ -92,6 +94,6 @@ def add_notifications(config, jobs):
                 }
             )
             if message:
-                job['extra']['notify']['email']['message'] = message
+                job['extra']['notify']['email']['content'] = message
 
         yield job