fix: never retry CancelledError under retry_if_not_exception_type

[MohammedAnasNathani]

Summary

Fixes #529.

retry_if_not_exception_type(ValueError) currently retries any non-ValueError, including asyncio.CancelledError. That breaks cancellation:

@retry(retry=retry_if_not_exception_type(ValueError), reraise=True, ...)
async def work():
    await asyncio.sleep(10)

await asyncio.wait_for(work(), 0.05)  # should stop; used to retry then finish

Default retry_if_exception_type() only retries Exception subclasses, so cancel already worked there. The bug is specific to the if_not / unless predicates.

Fix

Central helper _is_control_flow_exception — never retry:

• asyncio.CancelledError
• KeyboardInterrupt / SystemExit / GeneratorExit

Applied in:

• retry_if_not_exception_type
• retry_unless_exception_type

Tests

• wait_for + retry_if_not_exception_type → one attempt only
• direct CancelledError → not retried
• sync KeyboardInterrupt → not retried

Why this is important

Without this, any asyncio.timeout / wait_for around a tenacity-wrapped coroutine with a custom retry_if_not_exception_type can hang or run past the deadline.

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