Avoid redis lock's expire_time exceeding timeout.

After n heartbeats, the expireation time of the lock key becomes
(1 + 0.5n) * timeout! Therefore, when the lock holder performs a
long task and exits abnormally, the lock will not be automatically
released in time.

Change-Id: I2437071bb575e95083b0d57a6a0a33aaf8356113

setup.cfg

@@ -52,7 +52,7 @@ etcd3gw =
 zake =
   zake>=0.1.6 # Apache-2.0
 redis =
-  redis>=2.10.0 # MIT
+  redis>=3.1.0 # MIT
 postgresql =
   psycopg2>=2.5 # LGPL/ZPL
 mysql =

tooz/drivers/redis.py

@@ -110,7 +110,7 @@ class RedisLock(locking.Lock):
         with self._exclusive_access:
             if self.acquired:
                 with _translate_failures():
-                    self._lock.extend(self._lock.timeout)
+                    self._lock.reacquire()
                     return True
         return False