New 'mistune' thrown no attribute 'BlockGrammar'

[sebek98]

Hi,

It looks like the new version on the 'mistune' (2.0.0 released Dec 5, 2021) package has different API and it throws AttributeError: module 'mistune' has no attribute 'BlockGrammar'
Previous version (0.8.4 released Oct 18, 2018) looks correct and works fine.

`

Running Sphinx v4.1.2

Exception occurred:
File "/home/osboxes/proba/taf_inherited_members/venv/lib/python3.9/site-packages/m2r2.py", line 83, in
class RestBlockGrammar(mistune.BlockGrammar):
AttributeError: module 'mistune' has no attribute 'BlockGrammar'
The full traceback has been saved in /tmp/sphinx-err-3daao_tt.log, if you want to report the issue to the developers.
`

Pipdeptree shows that this is a dependency of m2r2 package:

`

m2r2==0.3.1

• docutils [required: Any, installed: 0.18.1]
• mistune [required: Any, installed: 2.0.0]
  pipdeptree==2.2.0
• pip [required: >=6.0.0, installed: 21.3.1]
  setuptools==58.3.0
  wheel==0.37.0
  `

Full sphinx log:
`

Sphinx version: 4.1.2
Python version: 3.9.5 (CPython)
Docutils version: 0.17.1 release
Jinja2 version: 3.0.3
Last messages:

Loaded extensions:
Traceback (most recent call last):
File "/home/osboxes/proba/taf_inherited_members/venv/lib/python3.9/site-packages/sphinx/cmd/build.py", line 276, in build_main
app = Sphinx(args.sourcedir, args.confdir, args.outputdir,
File "/home/osboxes/proba/taf_inherited_members/venv/lib/python3.9/site-packages/sphinx/application.py", line 237, in init
self.setup_extension(extension)
File "/home/osboxes/proba/taf_inherited_members/venv/lib/python3.9/site-packages/sphinx/application.py", line 393, in setup_extension
self.registry.load_extension(self, extname)
File "/home/osboxes/proba/taf_inherited_members/venv/lib/python3.9/site-packages/sphinx/registry.py", line 429, in load_extension
mod = import_module(extname)
File "/usr/lib/python3.9/importlib/init.py", line 127, in import_module
return _bootstrap._gcd_import(name[level:], package, level)
File "", line 1030, in _gcd_import
File "", line 1007, in _find_and_load
File "", line 986, in _find_and_load_unlocked
File "", line 680, in _load_unlocked
File "", line 855, in exec_module
File "", line 228, in _call_with_frames_removed
File "/home/osboxes/proba/taf_inherited_members/venv/lib/python3.9/site-packages/m2r2.py", line 83, in
class RestBlockGrammar(mistune.BlockGrammar):
AttributeError: module 'mistune' has no attribute 'BlockGrammar'
`

[CrossNox]

Duplicate of #40