@anon41087856, dt has been supporting my use of the ICC’s “preference perceptual intent” profile in the output color profile module, this is confirmed by loading jpegs into GIMP which then shows the embedded profile and asks if you want to change it.
Recent dt builds now produce the error message (in Terminal window) noted above, but having just done the GIMP test, these jpegs are also showing that the “preference perceptual intent” profile is present, despite the error message.
So it looks like the message is surplus to requirements.