git-cl: Make 'failed to add as cc' message less scary

BUG=665263

Change-Id: If72f3e5369ea0df170916c353be5188167c7aecb
Reviewed-on: https://chromium-review.googlesource.com/454977
Reviewed-by: Andrii Shyshkalov <tandrii@chromium.org>
Commit-Queue: Aaron Gable <agable@chromium.org>

gerrit_util.py

@@ -686,7 +686,7 @@ def AddReviewers(host, change, add=None, is_reviewer=True, notify=True):
       _ = ReadHttpJsonResponse(conn, ignore_404=False)
     except GerritError as e:
       if e.http_status == 422:  # "Unprocessable Entity"
-        LOGGER.warn('Failed to add "%s" as a %s' % (r, state.lower()))
+        LOGGER.warn('Note: "%s" not added as a %s' % (r, state.lower()))
         errors = True
       else:
         raise