_requireTroveisNotActive (BorrowerOperations.sol:633, :1140-1149), the FIRST gate on
the open path (MK-047).
It blocks only Status.active. A Trove closed by the owner, by liquidation or by
redemption is not active and CAN be reopened, so this is not "an address that has ever had
a Trove", it is "an address whose Trove is open right now".
Why an open would be rejected. Machine readable, stable strings, in CONTRACT CALL ORDER.
The order is
_openTrove's own, sobindingConstraintnames the gate the chain would hit first rather than the one this file happens to check first.