gh-89290: Add notes to the exception for an unmarshallable object - #160939

>>> import marshal
>>> class MyStr(str): pass
... marshal.dumps(compile("def f(): pass", MyStr("foo.py"), "exec"))
... 
Traceback (most recent call last):
  File "<python-input-1>", line 2, in <module>
    marshal.dumps(compile("def f(): pass", MyStr("foo.py"), "exec"))
    ~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
ValueError: cannot marshal MyStr objects

>>> import marshal
>>> class MyStr(str): pass
... 
>>> marshal.dumps(compile("def f(): pass", MyStr("foo.py"), "exec"))
Traceback (most recent call last):
  File "<python-input-2>", line 1, in <module>
    marshal.dumps(compile("def f(): pass", MyStr("foo.py"), "exec"))
    ~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
ValueError: cannot marshal MyStr objects
when marshalling co_filename of code object f (foo.py, line 1)
when marshalling tuple item 0
when marshalling co_consts of code object <module> (foo.py, line 1)