Explicitly:
pip install mstpylib --extra-index-url https://git.mst.edu/api/v4/projects/4927/packages/pypi/simple
Implicitly, add the following lines to requirements.txt:
--extra-index-url https://git.mst.edu/api/v4/projects/4927/packages/pypi/simple
mstpylib
Unfortunately we'll have to explicitly list the project_id integer until we can come up with a workaround. GitLab supplies a project_aliases endpoint, but unfortunately only for the premium version.