fix json dump in py3, and logger format

tensorpack/callbacks/summary.py

@@ -69,7 +69,7 @@ class StatHolder(object):
 
     def _write_stat(self):
         tmp_filename = self.filename + '.tmp'
-        with open(tmp_filename, 'wb') as f:
+        with open(tmp_filename, 'w') as f:
             json.dump(self.stat_history, f)
         os.rename(tmp_filename, self.filename)
 

tensorpack/utils/logger.py

@@ -55,6 +55,7 @@ def _set_file(path):
         info("Log file '{}' backuped to '{}'".format(path, backup_name))
     hdl = logging.FileHandler(
         filename=path, encoding='utf-8', mode='w')
+    hdl.setFormatter(MyFormatter(datefmt='%d %H:%M:%S'))
     logger.addHandler(hdl)
 
 def set_logger_dir(dirname, action=None):