caches: fixed issue with exception on handling non-ascii cache keys.

vcsserver/lib/rc_cache/backends.py

@@ -32,6 +32,7 b' from dogpile.cache.util import memoized_'
 from pyramid.settings import asbool
 
 from vcsserver.lib.memory_lru_dict import LRUDict, LRUDictDebug
+from vcsserver.utils import safe_str
 
 
 _default_max_size = 1024
@@ -264,7 +265,7 b' class BaseRedisBackend(redis_backend.Red'
 
     def get_mutex(self, key):
         if self.distributed_lock:
-            lock_key = redis_backend.u('_lock_{0}').format(key)
+            lock_key = redis_backend.u('_lock_{0}').format(safe_str(key))
             return get_mutex_lock(self.client, lock_key, self._lock_timeout,
                                   auto_renewal=self._lock_auto_renewal)
         else: