What does this error really mean?
Most of my tasks don't have start or end dates yet. In fact I have just 1 fixed date so far, with a couple of dates relative to it.
I get this error on one task that depends on three others (absolute references), none of which depend on any task with a date. If I comment either of two of them, the error goes away.
If I make that error go away, it uncovers another similar error a bit later, in a task that depends on another peer task (with a !relative reference). Again if I comment the depends statement, the error disappears. Then the project builds.
I can see in TaskScenario.rb that this error comes from postScheduleCheck which is described as "not essential". Yet, it stops the project building. Which makes it pretty essential to me...