Tests less dependent on network resources

[mccalluc]

Ideally, unit tests should be able to run off line, so we're not surprised when some third party service goes off-line. I temporarily lost connectivity and was surprised by this error:

    def test_convert_nb_to_pdf():
        notebook = (fixtures_path / "fake-executed.ipynb").read_text()
>       pdf = convert_nb_to_pdf(notebook)

tests/utils/test_converters.py:81:
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
dp_wizard/utils/converters.py:77: in convert_nb_to_pdf
    return convert_nb(python_nb, nbconvert.WebPDFExporter)
dp_wizard/utils/converters.py:95: in convert_nb
    (body, _resources) = exporter.from_notebook_node(notebook)
.venv-3.11/lib/python3.11/site-packages/nbconvert/exporters/webpdf.py:174: in from_notebook_node
    pdf_data = self.run_playwright(html)
.venv-3.11/lib/python3.11/site-packages/nbconvert/exporters/webpdf.py:163: in run_playwright
    pdf_data = pool.submit(run_coroutine, main(temp_file)).result()
/opt/homebrew/Cellar/[email protected]/3.11.7_1/Frameworks/Python.framework/Versions/3.11/lib/python3.11/concurrent/futures/_base.py:456: in result
    return self.__get_result()
/opt/homebrew/Cellar/[email protected]/3.11.7_1/Frameworks/Python.framework/Versions/3.11/lib/python3.11/concurrent/futures/_base.py:401: in __get_result
    raise self._exception
/opt/homebrew/Cellar/[email protected]/3.11.7_1/Frameworks/Python.framework/Versions/3.11/lib/python3.11/concurrent/futures/thread.py:58: in run
    result = self.fn(*self.args, **self.kwargs)
.venv-3.11/lib/python3.11/site-packages/nbconvert/exporters/webpdf.py:161: in run_coroutine
    return loop.run_until_complete(coro)
/opt/homebrew/Cellar/[email protected]/3.11.7_1/Frameworks/Python.framework/Versions/3.11/lib/python3.11/asyncio/base_events.py:653: in run_until_complete
    return future.result()
.venv-3.11/lib/python3.11/site-packages/nbconvert/exporters/webpdf.py:109: in main
    await page.goto(f"file://{temp_file.name}", wait_until="networkidle")
.venv-3.11/lib/python3.11/site-packages/playwright/async_api/_generated.py:8985: in goto
    await self._impl_obj.goto(
.venv-3.11/lib/python3.11/site-packages/playwright/_impl/_page.py:551: in goto
    return await self._main_frame.goto(**locals_to_params(locals()))
.venv-3.11/lib/python3.11/site-packages/playwright/_impl/_frame.py:145: in goto
    await self._channel.send("goto", locals_to_params(locals()))
.venv-3.11/lib/python3.11/site-packages/playwright/_impl/_connection.py:61: in send
    return await self._connection.wrap_api_call(
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

self = <playwright._impl._connection.Connection object at 0x1288a53d0>
cb = <function Channel.send.<locals>.<lambda> at 0x128ceb060>, is_internal = False

    async def wrap_api_call(
        self, cb: Callable[[], Any], is_internal: bool = False
    ) -> Any:
        if self._api_zone.get():
            return await cb()
        task = asyncio.current_task(self._loop)
        st: List[inspect.FrameInfo] = getattr(task, "__pw_stack__", inspect.stack())
        parsed_st = _extract_stack_trace_information_from_stack(st, is_internal)
        self._api_zone.set(parsed_st)
        try:
            return await cb()
        except Exception as error:
>           raise rewrite_error(error, f"{parsed_st['apiName']}: {error}") from None
E           playwright._impl._errors.TimeoutError: Page.goto: Timeout 30000ms exceeded.
E           Call log:
E             - navigating to "file:///var/folders/jm/40wztt291610f8pk5w0sw20r0000gq/T/tmp4gyfnnkg.html", waiting until "networkidle"

.venv-3.11/lib/python3.11/site-packages/playwright/_impl/_connection.py:528: TimeoutError

Apparently, playwright is used internally to render PDFs? and that code, in turn, depends on some other resource on the internet? Seems fragile, and if this tool could potentially be used with sensitive data, it would be really good to avoid random network connections!