Running notebooks with Python 3.8.3 causes Assertion errors

在 Python 3.8.3 下使用全新的 kernel 重现链接的 circuits_advanced/1_advanced_circuits.ipynb，然后检查 ipykernel/kernelbase.py 和 tornado/ioloop.py 中 traceback 的位置。与 Python 3.8.2 或 3.7.x 进行比较，在这些版本中 notebook 可以正常工作；完成标准是确定兼容性原因，并验证由此产生的 fix 或依赖项变更。

Since upgrading to the latest python release 3.8.3 on my system I have had issues running a notebook, specifically: https://github.com/Qiskit/qiskit-tutorials/blob/master/tutorials/circuits_advanced/1_advanced_circuits.ipynb Running that notebook when you run it from scratch on a fresh kernel it hangs on cell 8 and the jupyter notebook output logs multiple assertion errors:

[I 07:27:26.810 NotebookApp] Replaying 3 buffered messages
[IPKernelApp] ERROR | Exception in message handler:
Traceback (most recent call last):
  File "/tmp/test-tutorials/lib/python3.8/site-packages/ipykernel/kernelbase.py", line 268, in dispatch_shell
    yield gen.maybe_future(handler(stream, idents, msg))
  File "/tmp/test-tutorials/lib/python3.8/site-packages/tornado/gen.py", line 735, in run
    value = future.result()
  File "/tmp/test-tutorials/lib/python3.8/site-packages/tornado/gen.py", line 209, in wrapper
    yielded = next(result)
  File "/tmp/test-tutorials/lib/python3.8/site-packages/ipykernel/kernelbase.py", line 543, in execute_request
    self.do_execute(
  File "/tmp/test-tutorials/lib/python3.8/site-packages/tornado/gen.py", line 225, in wrapper
    runner = Runner(result, future, yielded)
  File "/tmp/test-tutorials/lib/python3.8/site-packages/tornado/gen.py", line 712, in __init__
    if self.handle_yield(first_yielded):
  File "/tmp/test-tutorials/lib/python3.8/site-packages/tornado/gen.py", line 789, in handle_yield
    self.io_loop.add_future(self.future, inner)
  File "/tmp/test-tutorials/lib/python3.8/site-packages/tornado/ioloop.py", line 693, in add_future
    assert is_future(future)
AssertionError
[IPKernelApp] ERROR | Exception in message handler:
Traceback (most recent call last):
  File "/tmp/test-tutorials/lib/python3.8/site-packages/ipykernel/kernelbase.py", line 268, in dispatch_shell
    yield gen.maybe_future(handler(stream, idents, msg))
  File "/tmp/test-tutorials/lib/python3.8/site-packages/tornado/gen.py", line 735, in run
    value = future.result()
  File "/tmp/test-tutorials/lib/python3.8/site-packages/tornado/gen.py", line 209, in wrapper
    yielded = next(result)
  File "/tmp/test-tutorials/lib/python3.8/site-packages/ipykernel/kernelbase.py", line 543, in execute_request
    self.do_execute(
  File "/tmp/test-tutorials/lib/python3.8/site-packages/tornado/gen.py", line 225, in wrapper
    runner = Runner(result, future, yielded)
  File "/tmp/test-tutorials/lib/python3.8/site-packages/tornado/gen.py", line 712, in __init__
    if self.handle_yield(first_yielded):
  File "/tmp/test-tutorials/lib/python3.8/site-packages/tornado/gen.py", line 789, in handle_yield
    self.io_loop.add_future(self.future, inner)
  File "/tmp/test-tutorials/lib/python3.8/site-packages/tornado/ioloop.py", line 693, in add_future
    assert is_future(future)
AssertionError
[IPKernelApp] ERROR | Exception in message handler:
Traceback (most recent call last):
  File "/tmp/test-tutorials/lib/python3.8/site-packages/ipykernel/kernelbase.py", line 268, in dispatch_shell
    yield gen.maybe_future(handler(stream, idents, msg))
  File "/tmp/test-tutorials/lib/python3.8/site-packages/tornado/gen.py", line 735, in run
    value = future.result()
  File "/tmp/test-tutorials/lib/python3.8/site-packages/tornado/gen.py", line 209, in wrapper
    yielded = next(result)
  File "/tmp/test-tutorials/lib/python3.8/site-packages/ipykernel/kernelbase.py", line 543, in execute_request
    self.do_execute(
  File "/tmp/test-tutorials/lib/python3.8/site-packages/tornado/gen.py", line 225, in wrapper
    runner = Runner(result, future, yielded)
  File "/tmp/test-tutorials/lib/python3.8/site-packages/tornado/gen.py", line 712, in __init__
    if self.handle_yield(first_yielded):
  File "/tmp/test-tutorials/lib/python3.8/site-packages/tornado/gen.py", line 789, in handle_yield
    self.io_loop.add_future(self.future, inner)
  File "/tmp/test-tutorials/lib/python3.8/site-packages/tornado/ioloop.py", line 693, in add_future
    assert is_future(future)
AssertionError
[IPKernelApp] ERROR | Exception in message handler:
Traceback (most recent call last):
  File "/tmp/test-tutorials/lib/python3.8/site-packages/ipykernel/kernelbase.py", line 268, in dispatch_shell
    yield gen.maybe_future(handler(stream, idents, msg))
  File "/tmp/test-tutorials/lib/python3.8/site-packages/tornado/gen.py", line 735, in run
    value = future.result()
  File "/tmp/test-tutorials/lib/python3.8/site-packages/tornado/gen.py", line 209, in wrapper
    yielded = next(result)
  File "/tmp/test-tutorials/lib/python3.8/site-packages/ipykernel/kernelbase.py", line 543, in execute_request
    self.do_execute(
  File "/tmp/test-tutorials/lib/python3.8/site-packages/tornado/gen.py", line 225, in wrapper
    runner = Runner(result, future, yielded)
  File "/tmp/test-tutorials/lib/python3.8/site-packages/tornado/gen.py", line 712, in __init__
    if self.handle_yield(first_yielded):
  File "/tmp/test-tutorials/lib/python3.8/site-packages/tornado/gen.py", line 789, in handle_yield
    self.io_loop.add_future(self.future, inner)
  File "/tmp/test-tutorials/lib/python3.8/site-packages/tornado/ioloop.py", line 693, in add_future
    assert is_future(future)
AssertionError

Downgrading python to 3.8.2 (or 3.7.x) fixes this. I've also confirmed it on other platforms (I run on linux, but mac users running 3.8.3 have had the same issue). I assume this is probably a bug in python or tornado, but I lack the domain expertise on the stack to be sure.