add logger in validation

tiramisu/setting.py

@@ -17,6 +17,7 @@
 # ____________________________________________________________
 from time import time
 from copy import copy
+from logging import getLogger
 import weakref
 from tiramisu.error import (RequirementError, PropertiesOptionError,
                             ConstError, ConfigError)
@@ -99,6 +100,9 @@ rw_append = set(['frozen', 'disabled', 'validator', 'hidden'])
 rw_remove = set(['permissive', 'everything_frozen', 'mandatory'])
 
 
+log = getLogger('tiramisu')
+
+
 # ____________________________________________________________
 class _NameSpace(object):
     """convenient class that emulates a module