Allow compilation on python 3.10.0a6

[Theelx]

It seems that pydebug.h and pyarena.h were moved from /Include/ to /Include/cpython/ in the latest 3.10 alpha (a6).

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[Theelx]

Just signed the CLA, waiting the "one business day" now for it to be processed.

[hauntsaninja]

Thank you for this!

[hauntsaninja]

https://docs.python.org/dev/whatsnew/3.10.html#id2 says we can just include Python.h instead, which we already do. So let's only include pydebug.h if PY_MINOR_VERSION < 10...
Actually, I just checked Python 3.5's Python.h (the oldest Python typed_ast supports) and it includes both pydebug and pyarena. So I think we can just remove the troublesome includes entirely?

[Theelx]

That's possible, I didn't think of that because I don't know C. I'll test that out.

[gvanrossum]

I've tested this with Python 3.10a6 in a few places, and it's not quite 100% successful.

1. On Windows 10 it works.
2. On macOS 11.2.2 it does not work. I get many errors during compilation including #error architecture not supported. Note that my Mac is an Intel Mac, but the compiler apparently tries to compile for the new Apple CPU as well, and fails. Now I realize I have an old version of Xcode installed, so I'll try to refresh that and see how it goes. (If anyone remembers how to install the latest command line compilers without first installing Xcode let me know -- it's an uncomfortably large download and I never use the UI.)

I'll get back here if I get it compiling on macOS.

[gvanrossum]

Well, according to https://devguide.python.org/setup/#macos-and-os-x I should just run xcode-select --install, which tells me to go use "Software Update" instead, which tells me I'm up to date. Still waiting for Xcode download to finish...

[Theelx]

Have you tried the previous version of my PR, where I encased the problematic includes in an if check for python 3.10? I don't know any C or anything in depth about compilers, so that might not work, but the way I see it, its worth a shot.

Edit: Could it be an incompatibility introduced by supporting the M1 chip? Have you tried this on other python versions that support M1?

[hauntsaninja]

This works fine for me on macOS 10.15.7, so I propose merging and figuring out support for Apple Silicon in another place.
I don't know much about Apple Silicon, but might be worth looking at what cibuildwheel does, e.g. does this get things compiling for you? https://github.com/joerick/cibuildwheel/blob/c9451facbd7a4bb54d580a093c9e381d524c6170/cibuildwheel/macos.py#L248

[gvanrossum]

Okay, will merge, and mark as closing #156. And I'll open a separate ticket for Apple Silicon.