Missing attributes found running mypy on the standard library

[emmatyping]

The following are missing from stubs:

• codecs
• pkgutil.read_code
• inspect.CO_COROUTINE
• inspect.CO_ASYNC_GENERATOR
• pickle.bytes_types
• pickle.decode_long
• tkinter.simpledialog
• pdb.Pdb
• msvcrt.setmode
• sre_compile.SRE_FLAG_*
• urrlib.request.HTTPError
• docutils.parsers.rst.Parser
• docutils.frontend
• multiprocessing.get_start_method
• multiprocessing.get_context
• multiprocessing.TimeoutError
• multiprocessing.AuthenticationError
• multiprocessing.BufferTooShort

There also seem to be several uses of _thread, but I'm not familiar with typeshed's policy with "private" modules.

[srittau]

urllib.request.HTTPError actually looks like a genuine problem, since HTTPError is defined in urllib.error. urllib.request does also not include it in __all__.

[srittau]

msvcrt.setmode() will be added in #4548.

[srittau]

I checked a few more items that exist now.

[srittau]

#4554 addresses most of these, with the exception of tkinter.simpledialog and docutils.*. The latter isn't part of the stdlib, so I wonder where this is referenced. There is already a stub for _thread, so this should also be fine.