If a cycle of dependencies is attempted to be enqueued into a pipeline
and at least one of the participating projects has a per-branch change queue
and the changes in the cycle are in different branches, it can be confusing
for users why the changes were not enqueued. This is even more likely to
happen with implicit cyclic dependencies such as those from Gerrit's
submitted-together feature (but can happen with any driver).
To aid users in this situation, report this situation back to the code
review system.
Change-Id: I26174849deab627b2cf91d75029c5a2674cc37d6
249ccc403b