Hello, The Designate project recently discovered that Wallaby docs builds were failing. This started happening because jinja2 newer than is specified in the constraints file was being installed, and there was a non backward compatible change that broke the doc builds. After some debugging we have determined the reason for this is that `tox -e docs` has two steps in its installation process. The first is the dependency installation which respects constraints and then after that is the installation of the package itself (in this case Designate). This second step does not supply constraints info, and it is expected that all dependencies of the package have been preinstalled by the first step. Where we get in trouble is that the docs requirements for projects like Designate (and we suspect others) are a subset of the package requirements necessary to install the packages. This means the second step in this install process discovers that many dependencies need to be installed and this happens without constraints allowing unexpected versions to be pulled in. To resolve this issue, make sure you are including the project requirements along with the doc requirements in your tox environment dependencies section[1]. This will allow pip to install all of the required dependencies, those required for the documentation generation and those for the project, to be all installed using the upper constraints. Thanks to clarkb and fungi for helping track down this issue and composing this email. [1] https://review.opendev.org/c/openstack/designate/+/836410/1/tox.ini