We use pip-tools to ensure all our dependencies use the same versions on all deployments.
To add a dependency, add it to either requirements.in or requirements-dev.in, then
run pip-compile requirements[-dev].in to generate the .txt file. Please make sure that
both the .in and .txt file changes are part of the commit when updating dependencies.
To update a dependency, use pip-compile --upgrade-package [package-name] requirements[-dev].in
For more details, please see the pip-tools docs on Github.