pull-requests: make sure to skip duplicates of reviewers via PR create method.

rhodecode/model/pull_request.py

@@ -442,8 +442,12 b' class PullRequestModel(BaseModel):'
         # members / reviewers
         for reviewer_object in reviewers:
             user_id, reasons, mandatory = reviewer_object
+            user = self._get_user(user_id)
 
-            user = self._get_user(user_id)
+            # skip duplicates
+            if user.user_id in reviewer_ids:
+                continue
+
             reviewer_ids.add(user.user_id)
 
             reviewer = PullRequestReviewers()