pyproject.toml: require Sphinx>=2.0.0 for doc feature

[Bastian-Krause]

Description
readthedocs installs Python package dependencies like this:

$ pip install --upgrade --no-cache-dir pip setuptools
$ pip install --upgrade --no-cache-dir pillow mock==1.0.1 alabaster>=0.7,<0.8,!=0.7.5 commonmark==0.9.1 recommonmark==0.5.0 sphinx<2 sphinx-rtd-theme<0.5 readthedocs-sphinx-ext<2.3 jinja2<3.1.0
$ pip install --upgrade --upgrade-strategy only-if-needed --no-cache-dir .[doc]

Until recently --upgrade-strategy was specified as eager, but now only-if-needed [1]. This results in Sphinx 1.8.6 being used.

This becomes an issue since Sphinx is not required directly by labgrid, but via sphinx_rtd_theme which loosely requires sphinx >=1.6,<8 [2]. This results in this readthedocs build error:

Exception occurred:
  File "[...]/labgrid/venv-rtd-debugging/lib/python3.11/site-packages/sphinx/ext/autodoc/__init__.py", line 82, in members_option
    return [x.strip() for x in arg.split(',')]
                               ^^^^^^^^^
AttributeError: 'bool' object has no attribute 'split'

We could make this work with Sphinx<2.0.0 [3]:

--- a/doc/conf.py
+++ b/doc/conf.py
@@ -179,7 +179,7 @@ texinfo_documents = [

 autodoc_member_order = 'bysource'
 autodoc_default_options = {
-        'special-members': True,
+        'special-members': None,
 }
 autodoc_mock_imports = ['onewire',
                         'txaio',

But even with this, another error and several warnings occur:

WARNING: Sphinx 1.x is deprecated with sphinx_rtd_theme, update to Sphinx 2.x or greater
WARNING: 'html4_writer' is deprecated with sphinx_rtd_theme

[...]/labgrid/venv-rtd-debugging/lib/python3.11/site-packages/sphinx/util/nodes.py:94: FutureWarning:
   The iterable returned by Node.traverse()
   will become an iterator instead of a list in Docutils > 0.16.
  for classifier in reversed(node.parent.traverse(nodes.classifier)):
[...]/labgrid/doc/getting_started.rst:393: WARNING: Error in "code-block" directive:
1 argument(s) required, 0 supplied.
Exception occurred:
  File "[...]/labgrid/venv-rtd-debugging/lib/python3.11/site-packages/sphinx/ext/napoleon/docstring.py", line 123, in __init__
    elif isinstance(obj, collections.Callable):  # type: ignore
                         ^^^^^^^^^^^^^^^^^^^^
AttributeError: module 'collections' has no attribute 'Callable'

It's not worth the effort to keep this backwards compatible, so simply require Sphinx>=2.0.0 in labgrid directly.

[1] readthedocs/readthedocs.org#10560
[2] https://github.com/readthedocs/sphinx_rtd_theme/blob/b5833585b25358be94918f13c50530e3e9237e7e/setup.cfg
[3] sphinx-doc/sphinx#5459

Checklist

• PR has been tested

[Bastian-Krause]

Failed rtd build: https://readthedocs.org/projects/labgrid/builds/21529558/

[codecov]

Codecov Report

Patch coverage has no change and project coverage change: -0.1% ⚠️

Comparison is base (2bfba1a) 62.9% compared to head (3517a22) 62.9%.

Additional details and impacted files

@@           Coverage Diff            @@
##           master   #1257     +/-   ##
========================================
- Coverage    62.9%   62.9%   -0.1%     
========================================
  Files         161     161             
  Lines       11861   11861             
========================================
- Hits         7470    7467      -3     
- Misses       4391    4394      +3     

see 1 file with indirect coverage changes

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