[FIX] name_get returns tuple

bzr revid: mat@openerp.com-20140506143834-od28gkhbpbhsgde4

addons/gamification/models/challenge.py

@@ -739,7 +739,7 @@ class gamification_challenge(osv.Model):
 
                 if rewarded_users:
                     user_names = self.pool['res.users'].name_get(cr, uid, rewarded_users, context=context)
-                    message_body += _("<br/>Reward (badge %s) for every succeeding user was sent to %s." % (challenge.reward_id.name, ", ".join([user for user in user_names])))
+                    message_body += _("<br/>Reward (badge %s) for every succeeding user was sent to %s." % (challenge.reward_id.name, ", ".join([name for (user_id, name) in user_names])))
                 else:
                     message_body += _("<br/>Nobody has succeeded to reach every goal, no badge is rewared for this challenge.")