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Seeing the following program, in the second assertRaises(), function "test_invalid_adpcm_state()" is recursively called. Then a fatal Python error shows up and the Python interpreter crashes. 
++++++++++++++++++++++++++++++++++++++
import unittest
import audioop
class TestAudioop(unittest.TestCase):
 pass
def test_invalid_adpcm_state():
 TestAudioop.assertRaises(TypeError, audioop.lin2adpcm, b'\x00', 1, 555)
 TestAudioop.assertRaises(test_invalid_adpcm_state(), audioop.adpcm2lin, b'\x00', 1, (0, (- 1)))
TestAudioop = TestAudioop()
test_invalid_adpcm_state()
+++++++++++++++++++++++++++++++++++++++
System Info: Ubuntu 16.04
Python Version: Python 3.9.1

Reproduced on master as well. Simplified script:
------------------------------------------
import unittest
def f():
 raise TypeError
class TestAudioop(unittest.TestCase):
 def test_invalid_adpcm_state(self):
 self.assertRaises(TypeError, f) 
 self.test_invalid_adpcm_state()
TestAudioop().test_invalid_adpcm_state()
------------------------------------------

Could you please tell me your secret method of getting the minimal script?
I will try to provide minimal ones in our following work.

3.9 crashes.
On master, I'm not seeing a crash, just a RecursionError.
>>> import unittest
>>> 
>>> def f():
... raise TypeError
... 
>>> class TestAudioop(unittest.TestCase):
... def test_invalid_adpcm_state(self):
... self.assertRaises(TypeError, f) 
... self.test_invalid_adpcm_state()
... 
>>> TestAudioop().test_invalid_adpcm_state()
Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
 File "<stdin>", line 4, in test_invalid_adpcm_state
 File "<stdin>", line 4, in test_invalid_adpcm_state
 File "<stdin>", line 4, in test_invalid_adpcm_state
 [Previous line repeated 992 more times]
 File "<stdin>", line 3, in test_invalid_adpcm_state
 File "/home/mark/repos/cpython/Lib/unittest/case.py", line 730, in assertRaises
 context = _AssertRaisesContext(expected_exception, self)
 File "/home/mark/repos/cpython/Lib/unittest/case.py", line 168, in __init__
 _BaseTestCaseContext.__init__(self, test_case)
RecursionError: maximum recursion depth exceeded

Yang - no secret really, just trial and error.
Mark - right I wasn't on master, sorry.

I think this was fixed by https://github.com/python/cpython/pull/23568
The root cause seems to be the same as #42500, so I'm going to backport https://github.com/python/cpython/pull/23568 to 3.9

#43186, #43187 also have recursive code that fails in 3.9 and recovers in 3.10. Am closing them in favor of this. Also suspect #43188, #43189, #43190 are duplicates. Yang, recheck after Mark does the backport here.