Pydoc fails with the codecs module in 3.5+. All works in 3.4.

$ ./python -m pydoc codecs
Traceback (most recent call last):
  File "/home/serhiy/py/cpython-3.5/Lib/runpy.py", line 170, in _run_module_as_main
    "__main__", mod_spec)
  File "/home/serhiy/py/cpython-3.5/Lib/runpy.py", line 85, in _run_code
    exec(code, run_globals)
  File "/home/serhiy/py/cpython-3.5/Lib/pydoc.py", line 2648, in <module>
    cli()
  File "/home/serhiy/py/cpython-3.5/Lib/pydoc.py", line 2613, in cli
    help.help(arg)
  File "/home/serhiy/py/cpython-3.5/Lib/pydoc.py", line 1895, in help
    elif request: doc(request, 'Help on %s:', output=self._output)
  File "/home/serhiy/py/cpython-3.5/Lib/pydoc.py", line 1632, in doc
    pager(render_doc(thing, title, forceload))
  File "/home/serhiy/py/cpython-3.5/Lib/pydoc.py", line 1625, in render_doc
    return title % desc + '\n\n' + renderer.document(object, name)
  File "/home/serhiy/py/cpython-3.5/Lib/pydoc.py", line 370, in document
    if inspect.ismodule(object): return self.docmodule(*args)
  File "/home/serhiy/py/cpython-3.5/Lib/pydoc.py", line 1160, in docmodule
    contents.append(self.document(value, key, name))
  File "/home/serhiy/py/cpython-3.5/Lib/pydoc.py", line 372, in document
    if inspect.isroutine(object): return self.docroutine(*args)
  File "/home/serhiy/py/cpython-3.5/Lib/pydoc.py", line 1345, in docroutine
    signature = inspect.signature(object)
  File "/home/serhiy/py/cpython-3.5/Lib/inspect.py", line 2988, in signature
    return Signature.from_callable(obj, follow_wrapped=follow_wrapped)
  File "/home/serhiy/py/cpython-3.5/Lib/inspect.py", line 2738, in from_callable
    follow_wrapper_chains=follow_wrapped)
  File "/home/serhiy/py/cpython-3.5/Lib/inspect.py", line 2229, in _signature_from_callable
    skip_bound_arg=skip_bound_arg)
  File "/home/serhiy/py/cpython-3.5/Lib/inspect.py", line 2061, in _signature_from_builtin
    return _signature_fromstr(cls, func, s, skip_bound_arg)
  File "/home/serhiy/py/cpython-3.5/Lib/inspect.py", line 2009, in _signature_fromstr
    p(name, default)
  File "/home/serhiy/py/cpython-3.5/Lib/inspect.py", line 1991, in p
    default_node = RewriteSymbolics().visit(default_node)
  File "/home/serhiy/py/cpython-3.5/Lib/ast.py", line 245, in visit
    return visitor(node)
  File "/home/serhiy/py/cpython-3.5/Lib/ast.py", line 310, in generic_visit
    new_node = self.visit(old_value)
  File "/home/serhiy/py/cpython-3.5/Lib/ast.py", line 245, in visit
    return visitor(node)
  File "/home/serhiy/py/cpython-3.5/Lib/inspect.py", line 1978, in visit_Attribute
    return wrap_value(value)
  File "/home/serhiy/py/cpython-3.5/Lib/inspect.py", line 1965, in wrap_value
    raise RuntimeError()
RuntimeError