Fix lock error (#3176)

Author: dvora-h

redis/exceptions.py

@@ -82,7 +82,7 @@ class LockError(RedisError, ValueError):
     # NOTE: For backwards compatibility, this class derives from ValueError.
     # This was originally chosen to behave like threading.Lock.
 
-    def __init__(self, message, lock_name=None):
+    def __init__(self, message=None, lock_name=None):
         self.message = message
         self.lock_name = lock_name