Make unittest.mock.create_autospec resilient against AttributeError on original object

Lib/unittest/test/testmock/testhelpers.py

@@ -651,6 +651,29 @@ class SpecSignatureTest(unittest.TestCase):
         mock.f.assert_called_with(3, 4)
 
 
+    def test_skip_attributeerrors(self):
+        class Raiser(object):
+            def __get__(self, obj, type=None):
+                if obj is None:
+                    raise AttributeError('Can only be accessed via an instance')
+
+        class RaiserClass(object):
+            raiser = Raiser()
+
+            @staticmethod
+            def existing(a, b):
+                return a + b
+
+        s = create_autospec(RaiserClass)
+        self.assertRaises(TypeError, lambda x: s.existing(1, 2, 3))
+        s.existing(1, 2)
+        self.assertRaises(AttributeError, lambda: s.nonexisting)
+
+        # check we can fetch the raiser attribute and it has no spec
+        obj = s.raiser
+        obj.foo, obj.bar
+
+
     def test_signature_class(self):
         class Foo(object):
             def __init__(self, a, b=3):