The reason is that the test suite is currently not properly working on F26+ so the vagrant environment will stay F25 until that is fixed.

This is blocked by https://github.com/libgit2/pygit2/issues/747 which while not providing a fix gave us a work around we now need to implement.

I'm closing this as invalid for now, we'll make the change when we can :)

Thanks for your ticket though, always appreciated :)