6.15.2: pytest is failing in `ipykernel/tests/test_debugger.py::test_stop_on_breakpoint` unit

I'm packaging your module as an rpm package so I'm using the typical PEP517 based build, install and test cycle used on building packages from non-root account.
- `python3 -sBm build -w --no-isolation`
- because I'm calling `build` with `--no-isolation` I'm using during all processes only locally installed modules
- install .whl file in
- run pytest with PYTHONPATH pointing to sitearch and sitelib inside

Here is pytest output:

```console
+ PYTHONPATH=/home/tkloczko/rpmbuild/BUILDROOT/python-ipykernel-6.15.2-2.fc35.x86_64/usr/lib64/python3.8/site-packages:/home/tkloczko/rpmbuild/BUILDROOT/python-ipykernel-6.15.2-2.fc35.x86_64/usr/lib/python3.8/site-packages
+ /usr/bin/pytest -ra
=========================================================================== test session starts ============================================================================
platform linux -- Python 3.8.13, pytest-7.1.2, pluggy-1.0.0
rootdir: /home/tkloczko/rpmbuild/BUILD/ipykernel-6.15.2, configfile: pyproject.toml, testpaths: ipykernel/tests, ipykernel/inprocess/tests
plugins: timeout-2.1.0, flaky-3.7.0
timeout: 300.0s
timeout method: signal
timeout func_only: False
collected 116 items

ipykernel/tests/test_async.py ..ss [ 3%]
ipykernel/tests/test_connect.py ..... [ 7%]
ipykernel/tests/test_debugger.py ...F.... [ 14%]
ipykernel/tests/test_embed_kernel.py ... [ 17%]
ipykernel/tests/test_eventloop.py . [ 18%]
ipykernel/tests/test_heartbeat.py .... [ 21%]
ipykernel/tests/test_io.py .. [ 23%]
ipykernel/tests/test_jsonutil.py sssss [ 27%]
ipykernel/tests/test_kernel.py .ss..........s..s...... [ 47%]
ipykernel/tests/test_kernelspec.py ............. [ 58%]
ipykernel/tests/test_message_spec.py ....................... [ 78%]
ipykernel/tests/test_pickleutil.py ..... [ 82%]
ipykernel/tests/test_start_kernel.py .. [ 84%]
ipykernel/tests/test_zmq_shell.py ...... [ 89%]
ipykernel/inprocess/tests/test_kernel.py s...... [ 95%]
ipykernel/inprocess/tests/test_kernelmanager.py ..... [100%]

================================================================================= FAILURES =================================================================================
_________________________________________________________________________ test_stop_on_breakpoint __________________________________________________________________________

kernel_with_debug =

def test_stop_on_breakpoint(kernel_with_debug):
code = """def f(a, b):
c = a + b
return c

f(2, 3)"""

r = wait_for_debug_request(kernel_with_debug, "dumpCell", {"code": code})
> source = r["body"]["sourcePath"]
E KeyError: 'body'

ipykernel/tests/test_debugger.py:138: KeyError
===Flaky Test Report===

test_embed_kernel_basic passed 1 out of the required 1 times. Success!
test_embed_kernel_namespace passed 1 out of the required 1 times. Success!
test_embed_kernel_reentrant passed 1 out of the required 1 times. Success!
test_subprocess_print passed 1 out of the required 1 times. Success!
test_subprocess_noprint passed 1 out of the required 1 times. Success!
test_subprocess_error passed 1 out of the required 1 times. Success!
test_ipython_start_kernel_userns passed 1 out of the required 1 times. Success!
test_ipython_start_kernel_no_userns passed 1 out of the required 1 times. Success!

===End Flaky Test Report===
=========================================================================== slowest 10 durations ===========================================================================
31.37s call ipykernel/tests/test_kernel.py::test_shutdown_subprocesses
6.32s call ipykernel/tests/test_async.py::test_async_interrupt[asyncio]
3.09s call ipykernel/tests/test_kernel.py::test_control_thread_priority
2.96s call ipykernel/tests/test_kernel.py::test_interrupt_during_input
2.82s call ipykernel/tests/test_kernel.py::test_subprocess_print
2.81s call ipykernel/tests/test_kernel.py::test_interrupt_with_message
2.53s call ipykernel/tests/test_message_spec.py::test_execute_stop_on_error
2.29s call ipykernel/tests/test_embed_kernel.py::test_embed_kernel_reentrant
2.03s call ipykernel/tests/test_kernel.py::test_interrupt_during_pdb_set_trace
1.78s setup ipykernel/tests/test_debugger.py::test_stop_on_breakpoint
========================================================================= short test summary info ==========================================================================
SKIPPED [1] ipykernel/tests/test_async.py:34: Requires trio
SKIPPED [1] ipykernel/tests/test_async.py:34: Requires curio
SKIPPED [1] ipykernel/tests/test_jsonutil.py:36: json_clean is a no-op
SKIPPED [1] ipykernel/tests/test_jsonutil.py:71: json_clean is a no-op
SKIPPED [1] ipykernel/tests/test_jsonutil.py:98: json_clean is a no-op
SKIPPED [1] ipykernel/tests/test_jsonutil.py:104: json_clean is a no-op
SKIPPED [1] ipykernel/tests/test_jsonutil.py:115: json_clean is a no-op
SKIPPED [1] ipykernel/tests/test_kernel.py:61: Currently don't capture during test as pytest does its own capturing
SKIPPED [1] ipykernel/tests/test_kernel.py:73: Currently don't capture during test as pytest does its own capturing
SKIPPED [1] ipykernel/tests/test_kernel.py:290: only run on Windows
SKIPPED [1] ipykernel/tests/test_kernel.py:349: test only on windows
SKIPPED [1] ipykernel/inprocess/tests/test_kernel.py:129: Currently don't capture during test as pytest does its own capturing
FAILED ipykernel/tests/test_debugger.py::test_stop_on_breakpoint - KeyError: 'body'
========================================================== 1 failed, 103 passed, 12 skipped in 103.54s (0:01:43) ===========================================================
```

Here is list of installed modules in build env

```console
Package Version
----------------------------- -----------------
alabaster 0.7.12
asttokens 2.0.5
attrs 22.1.0
Babel 2.10.2
backcall 0.2.0
Brlapi 0.8.3
build 0.8.0
charset-normalizer 2.1.0
codespell 2.1.0
cycler 0.11.0
debugpy 1.6.3
decorator 5.1.1
distro 1.7.0
docutils 0.18.1
editables 0.3
entrypoints 0.4
executing 0.8.3
extras 1.0.0
fixtures 4.0.0
flaky 3.7.0
fonttools 4.37.1
gpg 1.17.1-unknown
hatchling 1.8.1
idna 3.3
imagesize 1.4.1
importlib-metadata 4.12.0
iniconfig 1.1.1
ipykernel 6.15.1
ipyparallel 8.4.1
ipython 8.4.0
jedi 0.18.1
Jinja2 3.1.1
jupyter_client 7.3.5
jupyter_core 4.11.1
kiwisolver 1.4.4
libcomps 0.1.18
louis 3.22.0
markdown-it-py 2.1.0
MarkupSafe 2.1.1
matplotlib 3.5.3
matplotlib-inline 0.1.5
mdit-py-plugins 0.3.0
mdurl 0.1.1
myst-parser 0.18.0
nest-asyncio 1.5.5
numpy 1.23.1
olefile 0.46
packaging 21.3
parso 0.8.3
pathspec 0.9.0
pbr 5.9.0
pep517 0.12.0
pexpect 4.8.0
pickleshare 0.7.5
Pillow 9.2.0
pip 22.2.1
pluggy 1.0.0
prompt-toolkit 3.0.29
psutil 5.9.0
ptyprocess 0.7.0
pure-eval 0.2.2
py 1.11.0
Pygments 2.13.0
PyGObject 3.42.2
pyparsing 3.0.9
pytest 7.1.2
pytest-timeout 2.1.0
python-dateutil 2.8.2
pytz 2022.1
PyYAML 6.0
pyzmq 23.2.0
requests 2.28.1
rpm 4.17.0
setuptools 65.3.0
six 1.16.0
snowballstemmer 2.2.0
Sphinx 5.1.1
sphinxcontrib-applehelp 1.0.2.dev20220730
sphinxcontrib-devhelp 1.0.2.dev20220730
sphinxcontrib_github_alt 1.2
sphinxcontrib-htmlhelp 2.0.0
sphinxcontrib-jsmath 1.0.1.dev20220730
sphinxcontrib-qthelp 1.0.3.dev20220730
sphinxcontrib-serializinghtml 1.1.5
stack-data 0.5.0
testtools 2.5.0
tomli 2.0.1
tornado 6.2
tqdm 4.64.0
traitlets 5.3.0
typing_extensions 4.2.0
urllib3 1.26.12
wcwidth 0.2.5
wheel 0.37.1
zipp 3.8.1
```

Start with ipykernel/tests/test_debugger.py::test_stop_on_breakpoint and reproduce it using the reported PEP517 --no-isolation build, installed wheel, and pytest environment. Investigate why the dumpCell response lacks the expected body and sourcePath, then run the focused test and the full pytest suite to confirm the failure is resolved.

Vom Indexierungsmodell aus dem Issue-Text verfasst.