This will address the common mistake many asyncio users make:
an "except Exception" clause breaking Tasks cancellation.

In addition to this change, we stop inheriting asyncio.TimeoutError
and asyncio.InvalidStateError from their concurrent.futures.*
counterparts.  There's no point for these exceptions to share the
inheritance chain.

In 3.9 we'll focus on implementing supervisors and cancel scopes,
which should allow better handling of all exceptions, including
SystemExit and KeyboardInterrupt

…or (GH-21474)

#msg373510

[bpo-32528]()/#13528 changed `asyncio.CancelledError` such that it no longer inherits from `concurrent.futures.CancelledError`. As this affects existing code, specifically when catching the latter instead of the former in exception handling, it should be documented in the "What's new in 3.8?" document.

Automerge-Triggered-By: @1st1

…or (pythonGH-21474)

GH-msg373510

[bpo-32528]()/pythonGH-13528 changed `asyncio.CancelledError` such that it no longer inherits from `concurrent.futures.CancelledError`. As this affects existing code, specifically when catching the latter instead of the former in exception handling, it should be documented in the "What's new in 3.8?" document.

Automerge-Triggered-By: @1st1
(cherry picked from commit 2a51818)

Co-authored-by: JustAnotherArchivist <JustAnotherArchivist@users.noreply.github.com>

…or (pythonGH-21474)

GH-msg373510

[bpo-32528]()/pythonGH-13528 changed `asyncio.CancelledError` such that it no longer inherits from `concurrent.futures.CancelledError`. As this affects existing code, specifically when catching the latter instead of the former in exception handling, it should be documented in the "What's new in 3.8?" document.

Automerge-Triggered-By: @1st1
(cherry picked from commit 2a51818)

Co-authored-by: JustAnotherArchivist <JustAnotherArchivist@users.noreply.github.com>

…or (GH-21474)

GH-msg373510

[bpo-32528]()/GH-13528 changed `asyncio.CancelledError` such that it no longer inherits from `concurrent.futures.CancelledError`. As this affects existing code, specifically when catching the latter instead of the former in exception handling, it should be documented in the "What's new in 3.8?" document.

Automerge-Triggered-By: @1st1
(cherry picked from commit 2a51818)

Co-authored-by: JustAnotherArchivist <JustAnotherArchivist@users.noreply.github.com>

…or (pythonGH-21474)

GH-msg373510

[bpo-32528]()/pythonGH-13528 changed `asyncio.CancelledError` such that it no longer inherits from `concurrent.futures.CancelledError`. As this affects existing code, specifically when catching the latter instead of the former in exception handling, it should be documented in the "What's new in 3.8?" document.

Automerge-Triggered-By: @1st1
(cherry picked from commit 2a51818)

Co-authored-by: JustAnotherArchivist <JustAnotherArchivist@users.noreply.github.com>

…or (GH-21474)

GH-msg373510

[bpo-32528]()/GH-13528 changed `asyncio.CancelledError` such that it no longer inherits from `concurrent.futures.CancelledError`. As this affects existing code, specifically when catching the latter instead of the former in exception handling, it should be documented in the "What's new in 3.8?" document.

Automerge-Triggered-By: @1st1
(cherry picked from commit 2a51818)

Co-authored-by: JustAnotherArchivist <JustAnotherArchivist@users.noreply.github.com>

…or (pythonGH-21474)

#msg373510

[bpo-32528]()/python#13528 changed `asyncio.CancelledError` such that it no longer inherits from `concurrent.futures.CancelledError`. As this affects existing code, specifically when catching the latter instead of the former in exception handling, it should be documented in the "What's new in 3.8?" document.

Automerge-Triggered-By: @1st1

…or (pythonGH-21474)

#msg373510

[bpo-32528]()/python#13528 changed `asyncio.CancelledError` such that it no longer inherits from `concurrent.futures.CancelledError`. As this affects existing code, specifically when catching the latter instead of the former in exception handling, it should be documented in the "What's new in 3.8?" document.

Automerge-Triggered-By: @1st1

…or (pythonGH-21474)

#msg373510

[bpo-32528]()/python#13528 changed `asyncio.CancelledError` such that it no longer inherits from `concurrent.futures.CancelledError`. As this affects existing code, specifically when catching the latter instead of the former in exception handling, it should be documented in the "What's new in 3.8?" document.

Automerge-Triggered-By: @1st1