以下是在 redis 中创建、获取和释放锁：
import redis
redis_url = 'redis://127.0.0.1:6379/'
redis_conn = redis.from_url(redis_url)
l = redis_conn.lock('lock-test')
l.acquire()
l.release()
怎么会acquire()抛出以下错误？
Traceback (most recent call last):
File "C:/dev/myproj/test.py", line 11, in <module>
l.acquire()
File "C:\dev\myproj\venv_myproj\lib\site-packages\redis\lock.py", line 111, in acquire
if self.do_acquire(token):
File "C:\dev\myproj\venv_myproj\lib\site-packages\redis\lock.py", line 258, in do_acquire
client=self.redis))
File "C:\dev\myproj\venv_myproj\lib\site-packages\redis\client.py", line 2646, in __call__
return client.evalsha(self.sha, len(keys), *args)
File "C:\dev\myproj\venv_myproj\lib\site-packages\redis\client.py", line 1911, in evalsha
return self.execute_command('EVALSHA', sha, numkeys, *keys_and_args)
File "C:\dev\myproj\venv_myproj\lib\site-packages\redis\client.py", line 565, in execute_command
return self.parse_response(connection, command_name, **options)
File "C:\dev\myproj\venv_myproj\lib\site-packages\redis\client.py", line 577, in parse_response
response = connection.read_response()
File "C:\dev\myproj\venv_myproj\lib\site-packages\redis\connection.py", line 574, in read_response
raise response
redis.exceptions.ResponseError: unknown command 'EVALSHA'
我的设置：python 2.7.8，redis 2.4.5 64bit，win8