reviewers: use common function to obtain reviewers with filter of role.

rhodecode/model/comment.py

@@ -399,7 +399,7 b' class CommentsModel(BaseModel):'
             recipients += [pull_request_obj.author]
 
             # add the reviewers to notification
-            recipients += [x.user for x in pull_request_obj.reviewers]
+            recipients += [x.user for x in pull_request_obj.get_pull_request_reviewers()]
 
             pr_target_repo = pull_request_obj.target_repo
             pr_source_repo = pull_request_obj.source_repo

rhodecode/model/pull_request.py

@@ -1526,7 +1526,7 b' class PullRequestModel(BaseModel):'
                      commit_changes, file_changes):
 
         updating_user_id = updating_user.user_id
-        reviewers = set([x.user.user_id for x in pull_request.reviewers])
+        reviewers = set([x.user.user_id for x in pull_request.get_pull_request_reviewers()])
         # NOTE(marcink): send notification to all other users except to
         # person who updated the PR
         recipients = reviewers.difference(set([updating_user_id]))