Backed out changeset 7d3299d6e655

This is not compatible with python 3.5 and we want to support python 3.5 with cubicweb 3.27

--HG--
branch : 3.27

cubicweb/server/hook.py

@@ -248,7 +248,6 @@ Hooks and operations classes
 
 from logging import getLogger
 from itertools import chain
-from typing import Union, Tuple
 
 from logilab.common.decorators import classproperty, cached
 from logilab.common.logging_ext import set_log_methods
@@ -522,8 +521,8 @@ class Hook(AppObject):
     """
     __select__ = enabled_category()
     # set this in derivated classes
+    events = None
     category = None
-    events: Union[None, Tuple[str], Tuple[str, str]] = None
     order = 0
     # stop pylint from complaining about missing attributes in Hooks classes
     eidfrom = eidto = entity = rtype = repo = None