Fix #8655: autodoc: Crashes when object raises an exception on hasattr()

autodoc crashes when the target object raises an exception on
`hasattr()`.  The `hasattr()` function internally calls the
`obj.__getattr__()` or `obj.__getattribute__()` of the target object.
Hence the reaction can be changed on the target object.

This starts to use `safe_getattr()` to check the object is mocked or not
and to prevent an unexpected error.

CHANGES

@@ -16,6 +16,9 @@ Features added
 Bugs fixed
 ----------
 
+* #8655: autodoc: Failed to generate document if target module contains an
+  object that raises an exception on ``hasattr()``
+
 Testing
 --------