gh-109350: Fix outdated captured output in unittest.mock documentation (#109353)

Doc/library/unittest.mock-examples.rst

@@ -339,7 +339,7 @@ instantiate the class in those tests.
     >>> mock.old_method()
     Traceback (most recent call last):
        ...
-    AttributeError: object has no attribute 'old_method'
+    AttributeError: Mock object has no attribute 'old_method'. Did you mean: 'class_method'?
 
 Using a specification also enables a smarter matching of calls made to the
 mock, regardless of whether some parameters were passed as positional or
@@ -798,7 +798,8 @@ If your mock is only being called once you can use the
     >>> mock.foo_bar.assert_called_once_with('baz', spam='eggs')
     Traceback (most recent call last):
         ...
-    AssertionError: Expected to be called once. Called 2 times.
+    AssertionError: Expected 'foo_bar' to be called once. Called 2 times.
+    Calls: [call('baz', spam='eggs'), call()].
 
 Both ``assert_called_with`` and ``assert_called_once_with`` make assertions about
 the *most recent* call. If your mock is going to be called several times, and
@@ -927,8 +928,9 @@ Here's an example implementation:
     >>> c.assert_called_with(arg)
     Traceback (most recent call last):
         ...
-    AssertionError: Expected call: mock({1})
-    Actual call: mock(set())
+    AssertionError: expected call not found.
+    Expected: mock({1})
+    Actual: mock(set())
     >>> c.foo
     <CopyingMock name='mock.foo' id='...'>
 
@@ -1292,8 +1294,9 @@ sufficient:
     >>> mock.assert_called_with(Foo(1, 2))
     Traceback (most recent call last):
         ...
-    AssertionError: Expected: call(<__main__.Foo object at 0x...>)
-    Actual call: call(<__main__.Foo object at 0x...>)
+    AssertionError: expected call not found.
+    Expected: mock(<__main__.Foo object at 0x...>)
+    Actual: mock(<__main__.Foo object at 0x...>)
 
 A comparison function for our ``Foo`` class might look something like this: