So I installed the trac app (15.0) from ISO in a matter of minutes - as usual.
All up and running, although when I tried to save some settings "error: trac.ini could not be written"
trac was willing to save my settings.
Great thanks for the heads up on this!
Looks like a bug! Thanks for reporting. I've opened a bug report on our tracker. We'll aim to fix that for the next release.