It would be nice if the Skara PR bot could provide more information when a backport is not marked as clean. This question came up during the review of:

https://github.com/openjdk/jfx17u/pull/150

I note that when the Skara bot is unable to create a PR from the `/backport` command, it provides a list of conflicting files as helpful information to the developer. Maybe something similar could be done here?