Handle pyreadline failure (Windows + Python 3.10+)

[tianon]

Closes #2114

This is a bit hacky, but I'm not sure if there's a better way. I'm confident on the setup.py change to avoid even installing pyreadline on Python 3.10+ (which in itself is enough to fix the problem since then the fallback happens properly), but I added more code to handle the AttributeError for cases where pyreadline gets installed separately and thus import readline still pulls it in (I'm not sure which cases actually invoke the import pyreadline fallback code -- maybe older versions of pyreadline? older versions of Python's built-in readline module?).

[Kodiologist]

It looks like pyreadline is a dead library walking, so I would vote to just remove it entirely, and Windows users will have to use Cygwin if they want a decent CLI, as usual. So the branch except ImportError can be just docomplete = False. As for the other branch, can we do something more specific than checking for AttributeError? I feel like a lot of unforeseen bugs could trigger that.

[tianon]

Yeah, makes perfect sense -- I've just force pushed another go at this that I hope is more in line with what you have in mind. 😄

[Kodiologist]

Thanks. You can remove the comment referring to the Hy issue (the one referring to the pyreadline issue is useful, though, and should stay), and add a line to NEWS like "Fixed a crash on Windows due to Readline".

[tianon]

Absolutely -- I also added an explicit note about pyreadline, but happy to adjust again if you'd prefer not to even mention that. 👍

[liyiliuxingyu]

Please see this link.
#2114 (comment)