Merge pull request #207 from randsleadershipslack/shared-channel-fail…

…ures

handle slack channels shared with other teams

slacker.py

@@ -221,7 +221,10 @@ def get_channel_member_names(self, channel_name):
         returns an array of ["@member"] for members of the channel
         """
         members = self.get_channel_members_ids(channel_name)
-        return ["@" + self.users_by_id[x] for x in members]
+        # Need to check if user is in users_by_id because a channel may be shared
+        # across Slack teams and the other Slack team's members would not be in
+        # this Slack team's user/member list.
+        return ["@" + self.users_by_id[x] for x in members if x in self.users_by_id]
 
     def get_channel_info(self, channel_name):
         """