Factorize some code using ContextDecorator.

django/db/transaction.py

@@ -1,9 +1,7 @@
-from functools import wraps
-
 from django.db import (
     connections, DEFAULT_DB_ALIAS,
     DatabaseError, Error, ProgrammingError)
-from django.utils.decorators import available_attrs
+from django.utils.decorators import ContextDecorator
 
 
 class TransactionManagementError(ProgrammingError):
@@ -109,7 +107,7 @@ def set_rollback(rollback, using=None):
 # Decorators / context managers #
 #################################
 
-class Atomic(object):
+class Atomic(ContextDecorator):
     """
     This class guarantees the atomic execution of a given block.
 
@@ -285,13 +283,6 @@ class Atomic(object):
                 else:
                     connection.in_atomic_block = False
 
-    def __call__(self, func):
-        @wraps(func, assigned=available_attrs(func))
-        def inner(*args, **kwargs):
-            with self:
-                return func(*args, **kwargs)
-        return inner
-
 
 def atomic(using=None, savepoint=True):
     # Bare decorator: @atomic -- although the first argument is called