Missing information in CONTRIBUTING.rst

[sgpearse]

This has been reported before in #48, but I'm still struggling to get a local instance of a readthedocs server running in docker. Like other users have done in the past, I need a local instance to debug a broken build.

docker run --rm -t -i readthedocs/build:latest /bin/bash

followed by

cd ~docs
git clone https://github.com/readthedocs/template
cd template
make html

Results in the missing dependencies (sphinx, sphinx-build) problem reported in #48. @humitos reports that the following will install these missing dependencies, however these commands are outdated. For example, there is no python binary in readthedocs/build:latest. I've tried using python3 and venv in lieu of virtualenv, but that requires an apt install python3.12-venv which has permission issues.

python -m virtualenv --no-download --no-site-packages myenv
source ./myenv/bin/activate
pip install --use-wheel --upgrade Pygments==2.2.0 setuptools<40 docutils==0.13.1 mock==1.0.1 pillow==2.6.1 alabaster>=0.7<0.8!=0.7.5 commonmark==0.5.4 recommonmark==0.4.0 mkdocs==0.15.0
sphinx<2 sphinx-rtd-theme<0.3 readthedocs-sphinx-ext<0.6

Is there an updated procedure on how one can get a local docker container running the RTD build system so I can debug why my build is failing?