Error while building Tribler documentation: module 'mistune' has no attribute 'BlockGrammar'

[kozlovsky]

In our Jenkins PR-triggered job for building the documentation, we have the following line:
python -m sphinx -T -E -b html -d _build/doctrees -D language=en . _build/html
which currently produces the error:

Traceback (most recent call last):
  File "/home/jenkins/workspace/GH_Tribler_PR_Tests/PR_build_docs/venv/lib/python3.8/site-packages/sphinx/cmd/build.py", line 276, in build_main
    app = Sphinx(args.sourcedir, args.confdir, args.outputdir,
  File "/home/jenkins/workspace/GH_Tribler_PR_Tests/PR_build_docs/venv/lib/python3.8/site-packages/sphinx/application.py", line 237, in __init__
    self.setup_extension(extension)
  File "/home/jenkins/workspace/GH_Tribler_PR_Tests/PR_build_docs/venv/lib/python3.8/site-packages/sphinx/application.py", line 394, in setup_extension
    self.registry.load_extension(self, extname)
  File "/home/jenkins/workspace/GH_Tribler_PR_Tests/PR_build_docs/venv/lib/python3.8/site-packages/sphinx/registry.py", line 429, in load_extension
    mod = import_module(extname)
  File "/usr/lib/python3.8/importlib/__init__.py", line 127, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 1014, in _gcd_import
  File "<frozen importlib._bootstrap>", line 991, in _find_and_load
  File "<frozen importlib._bootstrap>", line 975, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 671, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 848, in exec_module
  File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
  File "/home/jenkins/workspace/GH_Tribler_PR_Tests/PR_build_docs/venv/lib/python3.8/site-packages/sphinxcontrib/openapi/__init__.py", line 13, in <module>
    from sphinxcontrib.openapi import renderers, directive
  File "/home/jenkins/workspace/GH_Tribler_PR_Tests/PR_build_docs/venv/lib/python3.8/site-packages/sphinxcontrib/openapi/renderers/__init__.py", line 4, in <module>
    from ._httpdomain_old import HttpdomainOldRenderer
  File "/home/jenkins/workspace/GH_Tribler_PR_Tests/PR_build_docs/venv/lib/python3.8/site-packages/sphinxcontrib/openapi/renderers/_httpdomain_old.py", line 6, in <module>
    from .. import openapi20, openapi30, utils
  File "/home/jenkins/workspace/GH_Tribler_PR_Tests/PR_build_docs/venv/lib/python3.8/site-packages/sphinxcontrib/openapi/openapi20.py", line 16, in <module>
    from sphinxcontrib.openapi import utils
  File "/home/jenkins/workspace/GH_Tribler_PR_Tests/PR_build_docs/venv/lib/python3.8/site-packages/sphinxcontrib/openapi/utils.py", line 20, in <module>
    from m2r import convert as convert_markdown
  File "/home/jenkins/workspace/GH_Tribler_PR_Tests/PR_build_docs/venv/lib/python3.8/site-packages/m2r.py", line 59, in <module>
    class RestBlockGrammar(mistune.BlockGrammar):
AttributeError: module 'mistune' has no attribute 'BlockGrammar'

The reason for the problem is the following bug of sphinxcontrib-openapi:
sphinx-contrib/openapi#121

And the reason for the bug is incompletely specified dependencies of sphinxcontrib-openapi.

To see the dependency graph, I installed the pipdeptree library:

> python -m pip install pipdeptree
> pipdeptree

With it, I can see the following dependency tree:

...
sphinxcontrib-openapi==0.7.0
  ...
  - m2r [required: >=0.2, installed: 0.2.1]
    ...
    - mistune [required: Any, installed: 2.0.0]
...

The m2r library requires the mistune library but does not specify the required version.

As it turns out, the API in version 2.0.0 of mistune has changed, and for the m2r library to work correctly, we need to use a previous version of mistune (0.8.4). With the mistune version 0.8.4, the documentation build works correctly.

To fix the problem, we need to specify the exact version of mistune in our doc requirements.

[pmuntyanu]

Thank you, Installing mistune==0.8.4 helped