Since abc._Abstract was replaces by a new type flags the regression test suite fails. I've added a new function inspect.isabstract(). Is the mmethod fine or should I check if object is a instance of type or subclass of object, too?
diff --git a/Lib/test/regrtest.py b/Lib/test/regrtest.py
index b6aa96b..dfb01ba 100755
--- a/Lib/test/regrtest.py
+++ b/Lib/test/regrtest.py
@@ -129,6 +129,7 @@
 import re
 import cStringIO
 import traceback
+from inspect import isabstract
 
 # I see no other way to suppress these warnings;
 # putting them in test_grammar.py has no effect:
@@ -649,7 +650,6 @@
 def dash_R(the_module, test, indirect_test, huntrleaks):
     # This code is hackish and inelegant, but it seems to do the job.
     import copy_reg, _abcoll
-    from abc import _Abstract
 
     if not hasattr(sys, 'gettotalrefcount'):
         raise Exception("Tracking reference leaks requires a debug build "
@@ -661,7 +661,7 @@
     pic = sys.path_importer_cache.copy()
     abcs = {}
     for abc in [getattr(_abcoll, a) for a in _abcoll.__all__]:
-        if not issubclass(abc, _Abstract):
+        if not isabstract(abc):
             continue
         for obj in abc.__subclasses__() + [abc]:
             abcs[obj] = obj._abc_registry.copy()
@@ -699,7 +699,6 @@
     import _strptime, linecache, dircache
     import urlparse, urllib, urllib2, mimetypes, doctest
     import struct, filecmp, _abcoll
-    from abc import _Abstract
     from distutils.dir_util import _path_created
 
     # Restore some original values.
@@ -714,7 +713,7 @@
 
     # Clear ABC registries, restoring previously saved ABC registries.
     for abc in [getattr(_abcoll, a) for a in _abcoll.__all__]:
-        if not issubclass(abc, _Abstract):
+        if not isabstract(abc):
             continue
         for obj in abc.__subclasses__() + [abc]:
             obj._abc_registry = abcs.get(obj, {}).copy()