bpo-37555: Ensure _call_matcher returns _Call object

Author: ElizabethU

Lib/unittest/mock.py

@@ -820,7 +820,7 @@ def _call_matcher(self, _call):
             else:
                 name, args, kwargs = _call
             try:
-                return name, sig.bind(*args, **kwargs)
+                return call(name, sig.bind(*args, **kwargs))
             except TypeError as e:
                 return e.with_traceback(None)
         else: