Fix a python3 issue in websocketclient

Change-Id: I4a07c4b9660cab67930d0acd643d128e91519089
Closes-Bug: #1845394
(cherry picked from commit 54b24b3a73)

zunclient/common/websocketclient/websocketclient.py

@@ -179,6 +179,8 @@ class BaseClient(object):
             self.quit = True
             return
 
+        if isinstance(data, bytes):
+            data = data.decode("utf-8")
         sys.stdout.write(data)
         sys.stdout.flush()