nbmake: NBMAKE INTERNAL ERROR: Exception ignored in socket

Describe the bug

I’m seeing the following error message in CI:

NBMAKE INTERNAL ERROR
Exception ignored in: <socket.socket fd=-1, family=AddressFamily.AF_UNIX, type=SocketKind.SOCK_STREAM, proto=0>

Traceback (most recent call last):
  File "/opt/hostedtoolcache/Python/3.10.6/x64/lib/python3.10/site-packages/jsonschema/exceptions.py", line 134, in _set
    for k, v in kwargs.items():
ResourceWarning: unclosed <socket.socket fd=27, family=AddressFamily.AF_UNIX, type=SocketKind.SOCK_STREAM, proto=0>

  File "/opt/hostedtoolcache/Python/3.10.6/x64/lib/python3.10/site-packages/_pytest/runner.py", line 338, in from_call
    result: Optional[TResult] = func()
  File "/opt/hostedtoolcache/Python/3.10.6/x64/lib/python3.10/site-packages/_pytest/runner.py", line [25](https://github.com/microsoft/torchgeo/runs/8172122269?check_suite_focus=true#step:5:26)9, in <lambda>
    lambda: ihook(item=item, **kwds), when=when, reraise=reraise
  File "/opt/hostedtoolcache/Python/3.10.6/x64/lib/python3.10/site-packages/pluggy/_hooks.py", line [26](https://github.com/microsoft/torchgeo/runs/8172122269?check_suite_focus=true#step:5:27)5, in __call__
    return self._hookexec(self.name, self.get_hookimpls(), kwargs, firstresult)
  File "/opt/hostedtoolcache/Python/3.10.6/x64/lib/python3.10/site-packages/pluggy/_manager.py", line 80, in _hookexec
    return self._inner_hookexec(hook_name, methods, kwargs, firstresult)
  File "/opt/hostedtoolcache/Python/3.10.6/x64/lib/python3.10/site-packages/pluggy/_callers.py", line 55, in _multicall
    gen.send(outcome)
  File "/opt/hostedtoolcache/Python/3.10.6/x64/lib/python3.10/site-packages/_pytest/unraisableexception.py", line 88, in pytest_runtest_call
    yield from unraisable_exception_runtest_hook()
  File "/opt/hostedtoolcache/Python/3.10.6/x64/lib/python3.10/site-packages/_pytest/unraisableexception.py", line 78, in unraisable_exception_runtest_hook
    warnings.warn(pytest.PytestUnraisableExceptionWarning(msg))

To Reproduce

1. See https://github.com/microsoft/torchgeo/runs/8172122269?check_suite_focus=true
2. Failing notebook is https://github.com/microsoft/torchgeo/blob/releases/v0.3/docs/tutorials/transforms.ipynb

Expected behavior

I would expect nbmake to either pass all tests, or inform me of what tests may have failed.

Desktop

• OS: Ubuntu 20.04
• Browser: Chrome
• Version: 1.3.4

Additional context

Seems similar to #71 but the error message is slightly different.