Fix propagation of CoreBluetooth errors

[rtoijala]

Errors from CBPeripeheralDelegate calls were being raised in the asyncio
event loop, but not in the correct task. In order to reach the user's
code, the error has to be passed through the event to the user call that
is awaiting the event.

Without these changes, e.g. ATT errors sent by the peripheral caused
error messages to be printed, but since the event that the user's call
was waiting on was never set, the user's code was blocked.

The implementation was adapted from #209

I have not been able to test with anything older than macOS Big Sur (11.4).

flake8, tox and pytest report loads of unrelated errors, but I did not see any
new errors from these changes.

Pull Request Guidelines for Bleak

Before you submit a pull request, check that it meets these guidelines:

1. If the pull request adds functionality, the docs should be updated.
2. Modify the CHANGELOG.rst, describing your changes as is specified by the
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   • Windows 10, version 16299 (Fall Creators Update) and greater
   • Linux distributions with BlueZ >= 5.43
   • OS X / macOS >= 10.11
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   consider making several PRs instead.
5. Feel free to add your name as a contributor to the AUTHORS.rst file!

[dlech]

I was noticing this was a problem recently too, so I'm glad you have taken the time to fix it!

Instead of creating our own class based on asyncio.Event, how about using asyncio.Future instead?

[rtoijala]

Updated to use asyncio.Future.

[dlech]

This looks great. It looks like there are some formatting issues. Since we need to fix that anyway, it would be nice to change the messages to f"" strings instead of using .format().

[dlech]

I've tested this now. Seems to be working. Thanks again!