docs: fix validation include line numbers

[thatlittleboy]

A small PR to fix the line numbers being included from the validate.py file. (currently ERROR_MSGS is not showing up properly on the docs)

[rossbar]

Thanks @thatlittleboy , nice catch. It'd be great if we could permalink this somehow so that it doesn't get out-of-date again whenever anyone edits the validate.py module. Off the top of my head I don't have any good idea how to do so - if anyone else does please share!

[thatlittleboy]

@rossbar I have a suggestion using the :start-after: and :end-before: options

https://www.sphinx-doc.org/en/master/usage/restructuredtext/directives.html#directive-literalinclude

doc/validation.rst

.. literalinclude:: ../numpydoc/validate.py
   :start-after: [validate-docs]
   :end-before: [validate-docs]

numpydoc/validate.py

# [validate-docs]
ERROR_MSG = {
    ...
}
# [validate-docs]

(unfortunately :pyobject: ERROR_MSGS doesn't work since pyobject only supports classes/functions/methods.)

cf. https://stackoverflow.com/a/31612552

[rossbar]

Thanks @thatlittleboy ! That is indeed a better solution. I went ahead and pushed up some minor fixups related to the missing sentinels, plus some additional code comments to explain what they're for.

[larsoner]

Thanks @thatlittleboy @rossbar !