Trivial Description
Currently there is one supported constraint in Thermos: 'order' or if you think of it another way, "on_finish".
Constraint(order = ['A', 'B']) means that 'B' should run after 'A' has completed, regardless of its terminal state. In a way, this could be translated to Constraint(on_success = ['A', 'B'], on_failure = ['A', 'B'])
But there shouldn't be anything preventing somebody from doing Constraint(on_success = ['A', 'B'], on_failure = ['A', 'C']). E.g. maybe process 'B' sends an e-mail that a deploy was successful, and process 'C' starts a rollback process.