No iteritems on py3.

Author: ionelmc

celery/concurrency/workhorse.py

@@ -190,7 +190,7 @@ def on_sigchld(self):
                     elif os.WIFSTOPPED(exit_code):
                         pending[pid] = os.WSTOPSIG(exit_code)
 
-        for pid, exit_code in pending.iteritems():
+        for pid, exit_code in pending.items():
             self.on_worker_exit(pid, exit_code)
 
     def on_worker_exit(self, pid, exit_code):