bpo-41768: Use getattr_static when adding mock spec

Since commit 77b3b77, class properties
are being called when adding mock specs and this can introduce side
effects for tests that are verifying state affected by code inside a
@Property.

This replaces the getattr call with a inspect.getattr_static call to
avoid executing class code as part of the mock speccing process.

Lib/unittest/mock.py

@@ -494,7 +494,7 @@ def _mock_add_spec(self, spec, spec_set, _spec_as_instance=False,
         _spec_asyncs = []
 
         for attr in dir(spec):
-            if iscoroutinefunction(getattr(spec, attr, None)):
+            if iscoroutinefunction(inspect.getattr_static(spec, attr, None)):
                 _spec_asyncs.append(attr)
 
         if spec is not None and not _is_list(spec):

Lib/unittest/test/testmock/testmock.py

@@ -38,6 +38,16 @@ def cmeth(cls, a, b, c, d=None): pass
     def smeth(a, b, c, d=None): pass
 
 
+class SomethingElse(object):
+    def __init__(self):
+        self._instance = None
+
+    @property
+    def instance(self):
+        if not self._instance:
+            self._instance = 'object'
+
+
 class Typos():
     autospect = None
     auto_spec = None
@@ -2249,6 +2259,12 @@ class Foo():
             f'{__name__}.Typos', autospect=True, set_spec=True, auto_spec=True):
             pass
 
+    def test_property_not_called_with_spec_mock(self):
+        obj = SomethingElse()
+        self.assertIsNone(obj._instance)
+        mock = Mock(spec=obj)
+        self.assertIsNone(obj._instance)
+
 
 if __name__ == '__main__':
     unittest.main()