Experiment with building on RTD

[jacobtomlinson]

I'm just playing around with using RTD to build, mainly for PR previews but could also switch the main hosting over too.

[jacobtomlinson]

I've been unable to get this to pass. The kernel always seems to die in the array notebook, perhaps the OOM killer isn't happy or something. It's a little hard to debug this on RTD so I'm going to close this out for now and I've opened #265 to track adding this in the future.

Running Sphinx v4.5.0
loading translations [en]... done
making output directory... done
WARNING: html_static_path entry '_static' does not exist
building [mo]: targets for 0 po files that are out of date
building [html]: targets for 7 source files that are out of date
updating environment: [new config] 7 added, 0 changed, 0 removed
reading sources... [ 14%] 00_overview
reading sources... [ 28%] 01_dataframe
reading sources... [ 42%] 02_array

Traceback (most recent call last):
  File "/home/docs/checkouts/readthedocs.org/user_builds/dask-tutorial/conda/251/lib/python3.9/site-packages/nbclient/client.py", line 780, in _async_poll_for_reply
    msg = await ensure_async(self.kc.shell_channel.get_msg(timeout=new_timeout))
  File "/home/docs/checkouts/readthedocs.org/user_builds/dask-tutorial/conda/251/lib/python3.9/site-packages/nbclient/util.py", line 97, in ensure_async
    result = await obj
  File "/home/docs/checkouts/readthedocs.org/user_builds/dask-tutorial/conda/251/lib/python3.9/site-packages/jupyter_client/channels.py", line 224, in get_msg
    ready = await self.socket.poll(timeout)
asyncio.exceptions.CancelledError

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/docs/checkouts/readthedocs.org/user_builds/dask-tutorial/conda/251/lib/python3.9/site-packages/nbclient/client.py", line 1006, in async_execute_cell
    exec_reply = await self.task_poll_for_reply
asyncio.exceptions.CancelledError

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/docs/checkouts/readthedocs.org/user_builds/dask-tutorial/conda/251/lib/python3.9/site-packages/nbsphinx.py", line 1043, in parse
    rststring, resources = exporter.from_notebook_node(nb, resources)
  File "/home/docs/checkouts/readthedocs.org/user_builds/dask-tutorial/conda/251/lib/python3.9/site-packages/nbsphinx.py", line 853, in from_notebook_node
    nb, resources = pp.preprocess(nb, resources)
  File "/home/docs/checkouts/readthedocs.org/user_builds/dask-tutorial/conda/251/lib/python3.9/site-packages/nbconvert/preprocessors/execute.py", line 89, in preprocess
    self.preprocess_cell(cell, resources, index)
  File "/home/docs/checkouts/readthedocs.org/user_builds/dask-tutorial/conda/251/lib/python3.9/site-packages/nbconvert/preprocessors/execute.py", line 110, in preprocess_cell
    cell = self.execute_cell(cell, index, store_history=True)
  File "/home/docs/checkouts/readthedocs.org/user_builds/dask-tutorial/conda/251/lib/python3.9/site-packages/nbclient/util.py", line 85, in wrapped
    return just_run(coro(*args, **kwargs))
  File "/home/docs/checkouts/readthedocs.org/user_builds/dask-tutorial/conda/251/lib/python3.9/site-packages/nbclient/util.py", line 60, in just_run
    return loop.run_until_complete(coro)
  File "/home/docs/checkouts/readthedocs.org/user_builds/dask-tutorial/conda/251/lib/python3.9/asyncio/base_events.py", line 647, in run_until_complete
    return future.result()
  File "/home/docs/checkouts/readthedocs.org/user_builds/dask-tutorial/conda/251/lib/python3.9/site-packages/nbclient/client.py", line 1010, in async_execute_cell
    raise DeadKernelError("Kernel died")
nbclient.exceptions.DeadKernelError: Kernel died

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/docs/checkouts/readthedocs.org/user_builds/dask-tutorial/conda/251/lib/python3.9/site-packages/sphinx/cmd/build.py", line 276, in build_main
    app.build(args.force_all, filenames)
  File "/home/docs/checkouts/readthedocs.org/user_builds/dask-tutorial/conda/251/lib/python3.9/site-packages/sphinx/application.py", line 330, in build
    self.builder.build_update()
  File "/home/docs/checkouts/readthedocs.org/user_builds/dask-tutorial/conda/251/lib/python3.9/site-packages/sphinx/builders/__init__.py", line 286, in build_update
    self.build(to_build,
  File "/home/docs/checkouts/readthedocs.org/user_builds/dask-tutorial/conda/251/lib/python3.9/site-packages/sphinx/builders/__init__.py", line 300, in build
    updated_docnames = set(self.read())
  File "/home/docs/checkouts/readthedocs.org/user_builds/dask-tutorial/conda/251/lib/python3.9/site-packages/sphinx/builders/__init__.py", line 407, in read
    self._read_serial(docnames)
  File "/home/docs/checkouts/readthedocs.org/user_builds/dask-tutorial/conda/251/lib/python3.9/site-packages/sphinx/builders/__init__.py", line 428, in _read_serial
    self.read_doc(docname)
  File "/home/docs/checkouts/readthedocs.org/user_builds/dask-tutorial/conda/251/lib/python3.9/site-packages/sphinx/builders/__init__.py", line 468, in read_doc
    doctree = read_doc(self.app, self.env, self.env.doc2path(docname))
  File "/home/docs/checkouts/readthedocs.org/user_builds/dask-tutorial/conda/251/lib/python3.9/site-packages/sphinx/io.py", line 181, in read_doc
    pub.publish()
  File "/home/docs/checkouts/readthedocs.org/user_builds/dask-tutorial/conda/251/lib/python3.9/site-packages/docutils/core.py", line 217, in publish
    self.document = self.reader.read(self.source, self.parser,
  File "/home/docs/checkouts/readthedocs.org/user_builds/dask-tutorial/conda/251/lib/python3.9/site-packages/sphinx/io.py", line 101, in read
    self.parse()
  File "/home/docs/checkouts/readthedocs.org/user_builds/dask-tutorial/conda/251/lib/python3.9/site-packages/docutils/readers/__init__.py", line 77, in parse
    self.parser.parse(self.input, document)
  File "/home/docs/checkouts/readthedocs.org/user_builds/dask-tutorial/conda/251/lib/python3.9/site-packages/nbsphinx.py", line 1052, in parse
    raise NotebookError(type(e).__name__ + ' in ' +
nbsphinx.NotebookError: DeadKernelError in 02_array.ipynb:
Kernel died

Notebook error:
DeadKernelError in 02_array.ipynb:
Kernel died