Class converted to invalid code

One of my test files (https://github.com/nedbat/coveragepy/blob/coverage-5.4/tests/test_testing.py) was converted into invalid code. I don't know what it is about that file that caused it, though it is a bit twisty: it's a test of test assert helper methods.

Here is a stripped-down file that shows the same behavior:

import pytest

from coverage.backunittest import TestCase

class TestingTest(TestCase):
    """Tests of helper methods on `backunittest.TestCase`."""

    def test_assert_count_equal(self):
        self.assertCountEqual(set(), set())
        with self.assertRaises(AssertionError):
            self.assertCountEqual({1,2,3}, set())
        with self.assertRaises(AssertionError):
            self.assertCountEqual({1,2,3}, {4,5,6})

Running unittest2pytest -w test_testing.py, the file becomes:

import pytest

from coverage.backunittest import TestCase
"""Tests of helper methods on `backunittest.TestCase`."""
deftest_assert_count_equal(self):
    self.assertCountEqual(set(), set())
    with pytest.raises(AssertionError):
        self.assertCountEqual({1,2,3}, set())
        withpytest.raises(AssertionError):
        self.assertCountEqual({1,2,3}, {4,5,6})

Start by running unittest2pytest -w test_testing.py against the reduced example and inspect the conversion path that handles TestCase classes and nested assertRaises blocks. Use tests/test_testing.py and the shown before-and-after output as the regression case; done means the converted file remains valid Python with the class, method, and nested context managers preserved.