Messages are required to get the right list of reviewers.

gcl.py

Index: gcl.py
diff --git a/gcl.py b/gcl.py
index 236b047a5b4715ffea9453f5d9873f8792246d34..ae852e9d7a8fb6e4e7c6142526464aba29cb7828 100755
--- a/gcl.py
+++ b/gcl.py
@@ -389,7 +389,7 @@ class ChangeInfo(object):
   def GetApprovingReviewers(self):
     """Returns the issue reviewers list from Rietveld."""
     return git_cl.get_approving_reviewers(
-        self.RpcServer().get_issue_properties(self.issue, False))
+        self.RpcServer().get_issue_properties(self.issue, True))
 
   def AddComment(self, comment):
     """Adds a comment for an issue on Rietveld.