FIX: Add mandatory attributes on enumerated_list

[cpitclaudel]

The doctrees that MyST generates are compatible with Sphinx but not with the normal Docutils pipeline. This PR fixes one of the incompatibilities. The first example of the API docs is enough to demonstrate the issue:

from myst_parser.main import to_docutils

document = to_docutils("""
Here's some *text*

1. a list

> a quote

{emphasis}`content`

```{sidebar} my sidebar
content
```
""")

from docutils.core import publish_from_doctree
print(publish_from_doctree(document, writer_name="latex").decode("utf-8"))

Traceback (most recent call last):
  File "./minimal.py", line 19, in <module>
    print(publish_from_doctree(document, writer_name="latex").decode("utf-8"))
  File "…/docutils/core.py", line 522, in publish_from_doctree
    return pub.publish(enable_exit_status=enable_exit_status)
  File "…/docutils/core.py", line 220, in publish
    output = self.writer.write(self.document, self.destination)
  File "…/docutils/writers/__init__.py", line 78, in write
    self.translate()
  File "…/docutils/writers/latex2e/__init__.py", line 251, in translate
    self.document.walkabout(visitor)
  File "…/docutils/nodes.py", line 214, in walkabout
    if child.walkabout(visitor):
  File "…/docutils/nodes.py", line 206, in walkabout
    visitor.dispatch_visit(self)
  File "…/docutils/nodes.py", line 1995, in dispatch_visit
    return method(node)
  File "…/docutils/writers/latex2e/__init__.py", line 2161, in visit_enumerated_list
    enumtype = types[node.get('enumtype' '')]
KeyError: None

The exact backtrace that docutils generates comes from a separate bug (https://sourceforge.net/p/docutils/patches/184/), but even with that fixed the LaTeX that gets generated is invalid, so it's probably worth fixing this here.

[chrisjsewell]

Thanks, you just need to fix the tests

[cpitclaudel]

Done, thanks

[codecov]

Codecov Report

Merging #418 (0e98b28) into master (f799bcf) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #418   +/-   ##
=======================================
  Coverage   90.77%   90.78%           
=======================================
  Files          16       16           
  Lines        1875     1877    +2     
=======================================
+ Hits         1702     1704    +2     
  Misses        173      173           

Flag	Coverage Δ
pytests	90.78% <100.00%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
myst_parser/docutils_renderer.py	92.75% <100.00%> (+0.02%)	⬆️

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[chrisjsewell]

thanks! look forward to the future docutils contributions 😄

[welcome]

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