Add `breathe` package to CI Python venvs.

It seems likely that at least one of the projects documented in the
GROMACS manual will want to incorporate documentation from C++ headers
(Doxygen) into the Sphinx pages. We can update the container build
script in advance so that the package will be available for
experimentation and testing after the next container rebuild.

See also #2698

diff --git a/admin/containers/scripted_gmx_docker_builds.py b/admin/containers/scripted_gmx_docker_builds.py
index d50ab66cde2771a1238134c1b24fed4f3161b63b..f0d2f3cc2b89965ee1a771bf49b025b32d0abe5a 100755 (executable)
--- a/admin/containers/scripted_gmx_docker_builds.py
+++ b/admin/containers/scripted_gmx_docker_builds.py
@@ -495,6 +495,7 @@ def prepare_venv(version: StrictVersion) -> typing.Sequence[str]:
     # WARNING: Please keep this list synchronized with python_packaging/requirements-test.txt
     # TODO: Get requirements.txt from an input argument.
     commands.append(f"""{venv_path}/bin/python -m pip install --upgrade \
+            'breathe' \
             'cmake>=3.16.3' \
             'flake8>=3.7.7' \
             'gcovr>=4.2' \