Update aiocontextvars to 0.2.0

[pyup-bot]

This PR updates aiocontextvars from 0.1.2 to 0.2.0.

Changelog

0.2.0

------------------

**This is a breaking change.** Most implementation is replaced with
``contextvars``. In Python 3.5 and 3.6, ``aiocontextvars`` depends on
``contextvars`` the PEP-567 backport in PyPI, and patches it to partially
support asyncio; in Python 3.7 ``aiocontextvars`` is only a delegate to the
built-in ``contextvars`` library.

* Modified ``ContextVar.set()`` to return a token.
* Added ``ContextVar.reset(token)``.
* Removed ``ContextVar.delete()``.
* Removed ``enable_inherit()`` and ``disable_inherit()``, inherit is always enabled.
* Added ``copy_context()`` and ``Context.run()``.
* Removed ``Context.current()`` and ``Context.inherited``.
* Fixed issue that ``set_event_loop(None)`` fails (contributed by J.J. Jackson in 10 11)

Links

• PyPI: https://pypi.org/project/aiocontextvars
• Changelog: https://pyup.io/changelogs/aiocontextvars/
• Repo: https://github.com/fantix/aiocontextvars

[coveralls]

Pull Request Test Coverage Report for Build 1182

• 1 of 1 (100.0%) changed or added relevant line in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.01%) to 98.251%

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Totals
Change from base Build 1174:	-0.01%
Covered Lines:	3932
Relevant Lines:	4002

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💛 - Coveralls

[wwwjfy]

@fantix Is it safe to merge? From the changelog, I assume some code to distinguish between contextvars and aiocontextvars can be removed.
But I don't see MagicStack/contextvars#2 closed, though you have a PR MagicStack/contextvars#11. I'm a bit confused. What's the status now?

[fantix]

It’s a bit weird how the tests passed when enable_inherit had been removed. I suppose it is not safe to merge yet.

MagicStack/contextvars#11 is very much the same as aiocontextvars 0.2, but that PR really requires some more discussion before it becomes final. I’d like to see how the proposal works as aiocontextvars 0.2 in GINO and how people thinks about the approach in action.

So after fixing the integration with 0.2, I’d like it merged before MagicStack/contextvars#11 have conclusion. And switching to contextvars shall be considered eventually after MagicStack/contextvars#2 is fixed.

[wwwjfy]

enable_inherit has do-nothing fallback when ImportError happens, if this is what you mean. I haven't checked the new implementation, but I assume it works the same way except enable_inherit. If this is the case, tests should not be affected.

[fantix]

Ah yes, then it is safe to merge. I'll remove the enable_inherit s.