Implementing a stub progress method in our GtkUi superclass does not help, because of the way extensions are registered when new UI instances are allocated, the progress extension can still monkey-patch our progress method and add progress bars to stdout.
The progress extension does three checks to verify it's not improperly generating progress bars, but all three are useless to us:
isinteractive - this must be true for us, else we cannot handle username/password prompts
debugflag - enables a lot of extra output, that we do not want to see or parse
quiet - disables much of the output we want to see