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bpo-31033: Improve the traceback for cancelled asyncio tasks (GH-19951)
When an asyncio.Task is cancelled, the exception traceback now starts with where the task was first interrupted. Previously, the traceback only had "depth one."
This commit is contained in:
Chris Jerdonek
GitHub
parent
d17f3d8315
commit
da742ba826
10 changed files with 290 additions and 80 deletions
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@ -10,6 +10,7 @@ import random
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import re
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import sys
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import textwrap
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import traceback
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import types
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import unittest
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import weakref
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@ -57,6 +58,22 @@ def format_coroutine(qualname, state, src, source_traceback, generator=False):
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return 'coro=<%s() %s at %s>' % (qualname, state, src)
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def get_innermost_context(exc):
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"""
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Return information about the innermost exception context in the chain.
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"""
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depth = 0
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while True:
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context = exc.__context__
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if context is None:
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break
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exc = context
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depth += 1
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return (type(exc), exc.args, depth)
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class Dummy:
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def __repr__(self):
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@ -111,9 +128,10 @@ class BaseTaskTests:
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self.assertEqual(t._cancel_message, None)
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t.cancel('my message')
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self.assertEqual(t._cancel_message, 'my message')
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with self.assertRaises(asyncio.CancelledError):
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self.loop.run_until_complete(t)
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self.assertEqual(t._cancel_message, 'my message')
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def test_task_cancel_message_setter(self):
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async def coro():
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@ -123,10 +141,8 @@ class BaseTaskTests:
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t._cancel_message = 'my new message'
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self.assertEqual(t._cancel_message, 'my new message')
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# Also check that the value is used for cancel().
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with self.assertRaises(asyncio.CancelledError):
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self.loop.run_until_complete(t)
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self.assertEqual(t._cancel_message, 'my new message')
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def test_task_del_collect(self):
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class Evil:
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@ -548,8 +564,8 @@ class BaseTaskTests:
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def test_cancel_with_message_then_future_result(self):
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# Test Future.result() after calling cancel() with a message.
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cases = [
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((), ('',)),
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((None,), ('',)),
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((), ()),
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((None,), ()),
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(('my message',), ('my message',)),
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# Non-string values should roundtrip.
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((5,), (5,)),
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@ -573,13 +589,17 @@ class BaseTaskTests:
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with self.assertRaises(asyncio.CancelledError) as cm:
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loop.run_until_complete(task)
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exc = cm.exception
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self.assertEqual(exc.args, expected_args)
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self.assertEqual(exc.args, ())
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actual = get_innermost_context(exc)
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self.assertEqual(actual,
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(asyncio.CancelledError, expected_args, 2))
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def test_cancel_with_message_then_future_exception(self):
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# Test Future.exception() after calling cancel() with a message.
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cases = [
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((), ('',)),
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((None,), ('',)),
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((), ()),
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((None,), ()),
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(('my message',), ('my message',)),
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# Non-string values should roundtrip.
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((5,), (5,)),
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@ -603,7 +623,11 @@ class BaseTaskTests:
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with self.assertRaises(asyncio.CancelledError) as cm:
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loop.run_until_complete(task)
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exc = cm.exception
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self.assertEqual(exc.args, expected_args)
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self.assertEqual(exc.args, ())
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actual = get_innermost_context(exc)
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self.assertEqual(actual,
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(asyncio.CancelledError, expected_args, 2))
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def test_cancel_with_message_before_starting_task(self):
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loop = asyncio.new_event_loop()
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@ -623,7 +647,11 @@ class BaseTaskTests:
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with self.assertRaises(asyncio.CancelledError) as cm:
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loop.run_until_complete(task)
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exc = cm.exception
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self.assertEqual(exc.args, ('my message',))
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self.assertEqual(exc.args, ())
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actual = get_innermost_context(exc)
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self.assertEqual(actual,
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(asyncio.CancelledError, ('my message',), 2))
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def test_cancel_yield(self):
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with self.assertWarns(DeprecationWarning):
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@ -805,6 +833,66 @@ class BaseTaskTests:
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self.assertTrue(nested_task.cancelled())
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self.assertTrue(fut.cancelled())
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def assert_text_contains(self, text, substr):
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if substr not in text:
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raise RuntimeError(f'text {substr!r} not found in:\n>>>{text}<<<')
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def test_cancel_traceback_for_future_result(self):
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# When calling Future.result() on a cancelled task, check that the
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# line of code that was interrupted is included in the traceback.
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loop = asyncio.new_event_loop()
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self.set_event_loop(loop)
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async def nested():
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# This will get cancelled immediately.
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await asyncio.sleep(10)
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async def coro():
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task = self.new_task(loop, nested())
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await asyncio.sleep(0)
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task.cancel()
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await task # search target
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task = self.new_task(loop, coro())
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try:
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loop.run_until_complete(task)
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except asyncio.CancelledError:
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tb = traceback.format_exc()
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self.assert_text_contains(tb, "await asyncio.sleep(10)")
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# The intermediate await should also be included.
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self.assert_text_contains(tb, "await task # search target")
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else:
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self.fail('CancelledError did not occur')
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def test_cancel_traceback_for_future_exception(self):
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# When calling Future.exception() on a cancelled task, check that the
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# line of code that was interrupted is included in the traceback.
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loop = asyncio.new_event_loop()
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self.set_event_loop(loop)
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async def nested():
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# This will get cancelled immediately.
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await asyncio.sleep(10)
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async def coro():
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task = self.new_task(loop, nested())
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await asyncio.sleep(0)
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task.cancel()
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done, pending = await asyncio.wait([task])
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task.exception() # search target
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task = self.new_task(loop, coro())
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try:
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loop.run_until_complete(task)
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except asyncio.CancelledError:
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tb = traceback.format_exc()
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self.assert_text_contains(tb, "await asyncio.sleep(10)")
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# The intermediate await should also be included.
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self.assert_text_contains(tb,
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"task.exception() # search target")
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else:
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self.fail('CancelledError did not occur')
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def test_stop_while_run_in_complete(self):
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def gen():
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@ -2391,15 +2479,14 @@ class BaseTaskTests:
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def test_cancel_gather_2(self):
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cases = [
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((), ('',)),
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((None,), ('',)),
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((), ()),
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((None,), ()),
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(('my message',), ('my message',)),
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# Non-string values should roundtrip.
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((5,), (5,)),
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]
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for cancel_args, expected_args in cases:
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with self.subTest(cancel_args=cancel_args):
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loop = asyncio.new_event_loop()
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self.addCleanup(loop.close)
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@ -2417,15 +2504,20 @@ class BaseTaskTests:
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qwe = self.new_task(loop, test())
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await asyncio.sleep(0.2)
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qwe.cancel(*cancel_args)
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try:
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await qwe
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except asyncio.CancelledError as exc:
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self.assertEqual(exc.args, expected_args)
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else:
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self.fail('gather did not propagate the cancellation '
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'request')
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await qwe
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loop.run_until_complete(main())
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try:
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loop.run_until_complete(main())
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except asyncio.CancelledError as exc:
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self.assertEqual(exc.args, ())
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exc_type, exc_args, depth = get_innermost_context(exc)
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self.assertEqual((exc_type, exc_args),
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(asyncio.CancelledError, expected_args))
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# The exact traceback seems to vary in CI.
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self.assertIn(depth, (2, 3))
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else:
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self.fail('gather did not propagate the cancellation '
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'request')
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def test_exception_traceback(self):
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# See http://bugs.python.org/issue28843
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