A Database-based knowledge back-end built on and for INDRA. The INDRA Database is a service that can be set up by any user with their own content and knowledge access. Our implementation of the database is the back-end to many of our projects, providing a vast and detailed knowledge base derived from many resources.
This PR adds a missing requirement to setup since it's required by downstream dependencies, see e.g., https://travis-ci.com/github/indralab/emmaa/builds/203149488.