fix yolov3 subprocess not exit (#2886)

* fix yolov3 subprocess not exit

* refine print

PaddleCV/yolov3/data_utils.py

@@ -2,6 +2,7 @@
 This code is based on https://github.com/fchollet/keras/blob/master/keras/utils/data_utils.py
 """
 
+import os
 import sys
 import signal
 import time
@@ -19,7 +20,13 @@ def _reader_quit(signum, frame):
     print("Reader process exit.")
     sys.exit()
 
+def _term_group(sig_num, frame):
+    print('pid {} terminated, terminate group '
+          '{}...'.format(os.getpid(), os.getpgrp()))
+    os.killpg(os.getpgid(os.getpid()), signal.SIGKILL)
+
 signal.signal(signal.SIGTERM, _reader_quit)
+signal.signal(signal.SIGINT, _term_group)
 
 
 class GeneratorEnqueuer(object):