add SlaveError for slave's length

tiramisu/setting.py

@@ -250,7 +250,7 @@ class Setting(object):
         if opt_or_descr in self._cache:
             t = time()
             props, raise_text, created = self._cache[opt_or_descr]
-            if t - created < expires_time:
+            if t < created:
                 properties = props
                 is_cached = True
         if not is_cached:
@@ -318,7 +318,7 @@ class Setting(object):
 
     def _set_cache(self, opt, props, raise_text):
         if self.has_property('expire'):
-            self._cache[opt] = (props, raise_text, time())
+            self._cache[opt] = (props, raise_text, time() + expires_time)
 
     def reset_cache(self):
         self._cache = {}