[ckan#3126] don't check if methodcaller is available

- `operator.methodcaller` was implemented in python2.7. Now that ckan
  only supports 2.7 it is no longer required to check if the import is
  possible or not. We can besure that it is there.

ckan/model/extension.py

@@ -4,23 +4,17 @@
 Provides bridges between the model and plugin PluginImplementationss
 """
 import logging
+from operator import methodcaller
 
 from sqlalchemy.orm.interfaces import MapperExtension
 from sqlalchemy.orm.session import SessionExtension
 
 import ckan.plugins as plugins
 
-try:
-    from operator import methodcaller
-except ImportError:
-    def methodcaller(name, *args, **kwargs):
-        "Replaces stdlib operator.methodcaller in python <2.6"
-        def caller(obj):
-            return getattr(obj, name)(*args, **kwargs)
-        return caller
 
 log = logging.getLogger(__name__)
 
+
 class ObserverNotifier(object):
     """
     Mixin for hooking into SQLAlchemy
@@ -93,7 +87,6 @@ def notify_observers(self, func):
         for observer in plugins.PluginImplementations(plugins.ISession):
             func(observer)
 
-
     def after_begin(self, session, transaction, connection):
         return self.notify_observers(
             methodcaller('after_begin', session, transaction, connection)
@@ -123,4 +116,3 @@ def after_rollback(self, session):
         return self.notify_observers(
             methodcaller('after_rollback', session)
         )
-