$ git --version
git version 2.30.0

======================================================================
ERROR: test_index_file_diffing (test.test_index.TestIndex)
----------------------------------------------------------------------
Traceback (most recent call last):
 File "/tmp/GitPython/test/lib/helper.py", line 140, in repo_creator
 return func(self, rw_repo)
 File "/tmp/GitPython/test/test_index.py", line 378, in test_index_file_diffing
 self.assertRaises(CheckoutError, index.checkout, "doesnt_exist_ever.txt.that")
 File "/usr/lib/python3.9/unittest/case.py", line 733, in assertRaises
 return context.handle('assertRaises', args, kwargs)
 File "/usr/lib/python3.9/unittest/case.py", line 201, in handle
 callable_obj(*args, **kwargs)
 File "/tmp/GitPython/git/index/util.py", line 76, in check_default_index
 return func(self, *args, **kwargs)
 File "/tmp/GitPython/git/index/base.py", line 1133, in checkout
 self._flush_stdin_and_wait(proc, ignore_stdout=True)
 File "/tmp/GitPython/git/index/base.py", line 980, in _flush_stdin_and_wait
 proc.wait()
 File "/tmp/GitPython/git/cmd.py", line 408, in wait
 raise GitCommandError(self.args, status, errstr)
git.exc.GitCommandError: Cmd('/usr/bin/git') failed due to: exit code(1)
 cmdline: /usr/bin/git checkout-index --index --stdin
 stderr: 'git checkout-index: doesnt_exist_ever.txt.that is not in the cache
'