feat(migration): add a migration script to warn about incompatibility of cwtags.

This is needed because a lot of people can waste a lot of time resolving
this issue: !208
in cwtags ; because of a monkeypatch.

see: cwtags!1
related: #367

--HG--
branch : 3.32
8 jobs for branch/3.32 in 89 minutes and 30 seconds (queued for 10 seconds)
Name Stage Failure
failed
build_doc Lint There has been a timeout failure or the job got stuck. Check your timeout limits or try again
Collecting backports.entry-points-selectable>=1.0.4
Downloading backports.entry_points_selectable-1.1.0-py2.py3-none-any.whl (6.2 kB)
Installing collected packages: six, pyparsing, platformdirs, filelock, distlib, backports.entry-points-selectable, virtualenv, toml, py, pluggy, packaging, tox
Successfully installed backports.entry-points-selectable-1.1.0 distlib-0.3.2 filelock-3.0.12 packaging-21.0 platformdirs-2.2.0 pluggy-0.13.1 py-1.10.0 pyparsing-2.4.7 six-1.16.0 toml-0.10.2 tox-3.24.1 virtualenv-20.7.2
$ tox -e doc
WARNING: Running pip as the 'root' user can result in broken permissions and conflicting behaviour with the system package manager. It is recommended to use a virtual environment instead: https://pip.pypa.io/warnings/venv
WARNING: You are using pip version 21.1.3; however, version 21.2.4 is available.
You should consider upgrading via the '/usr/local/bin/python -m pip install --upgrade pip' command.
doc create: /builds/cubicweb/cubicweb/.tox/doc
doc installdeps: sphinx, -r/builds/cubicweb/cubicweb/requirements/doc.txt