fix queue.empty block for summary

mindspore/train/summary/_writer_pool.py

@@ -16,6 +16,7 @@
 import os
 import time
 import signal
+import queue
 from collections import deque
 
 import psutil
@@ -108,14 +109,17 @@ class WriterPool(ctx.Process):
                     for plugin, data in deq.popleft().get():
                         self._write(plugin, data)
 
-                if not self._queue.empty():
-                    action, data = self._queue.get()
+                try:
+                    action, data = self._queue.get(block=False)
                     if action == 'WRITE':
                         deq.append(pool.apply_async(_pack_data, (data, time.time())))
                     elif action == 'FLUSH':
                         self._flush()
                     elif action == 'END':
                         break
+                except queue.Empty:
+                    pass
+
             for result in deq:
                 for plugin, data in result.get():
                     self._write(plugin, data)