Aio-pika

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* Prevent 'Task exception was never retrieved' 524
If future.exception() is not called (even on cancelled futures), it seems Python
will then log 'Task exception was never retrieved'. Rewriting this logic
slightly should hopefully achieve the same functionality while
preventing the Python errors.
* Avoid implicitly depending on setuptools 526

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* fix README badge
* upgrade requirements

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* RPCs: Show exceptions on Host (remote side) 503
* Fixed queue_name was set as channel_name for `patterns/master.py` 523

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* Do not nack if consumer is no_ack in QueueIterator 521

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* change classifiers in pyproject.toml

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The main goal of this release is the migration to `poetry` and stronger type
checking with mypy.

User code should remain compatible, just test it with mypy. The tests still
work the same, without public API changes, this indicates that your code
should work without changes, but does not prove it.

Deprecations

* `aio_pika.message.HeaderProxy` - removed
* `aio_pika.message.header_converter` - removed
* `aio_pika.message.format_headers` - removed
* `aio_pika.message.Message.headers_raw` - prints deprecation warning
* `aio_pika.abc.AbstractMessage.headers_raw` - removed