setup.cfg: Force astroid version to 2.15.7

[spencer-tb]

What was wrong?

Running tox -e doc was failing as the astroid version is now automatically bumped up to 3.0.0.

This is the error:

Running Sphinx v4.0.2
making output directory... done

Extension error (autoapi.extension):
Handler <function run_autoapi at 0x7f9658043f70> for event 'builder-inited' threw an exception (exception: 'Module' object has no attribute 'doc')
[AutoAPI] Reading files... [  0%] /home/runner/work/execution-specs/execution-specs/src/ethereum/ethash.py
doc: exit 2 (2.32 seconds) /home/runner/work/execution-specs/execution-specs> sphinx-build -j auto -t stage0 -d /home/runner/work/execution-specs/execution-specs/.tox/docs/stage0_doctree doc /home/runner/work/execution-specs/execution-specs/.tox/docs/stage0_out --color -W -brpickle pid=1866
.pkg: _exit> python /opt/hostedtoolcache/Python/3.8.18/x64/lib/python3.8/site-packages/pyproject_api/_backend.py True setuptools.build_meta
  doc: FAIL code 2 (24.99=setup[22.67]+cmd[2.32] seconds)
  evaluation failed :( (25.43 seconds)
Error: Process completed with exit code 2.

More error logs can be found in the last GitHub Pages run -> https://github.com/ethereum/execution-specs/actions/runs/6324911221/job/17175336696

How was it fixed?

Forcing astroid==2.15.7 wtihin setup.cfg resolves the issue.

Cute Animal Picture

[petertdavies]

Good spot. Thanks.