Comment 10 for bug 1725222

I believe this was discussed at the time with MySQL upstream. Although the 5.5 to 5.7 upgrade isn't an officially supported upgrade path by upstream, I think when we discussed it we concluded that it would be fine for moving a default installation of MySQL 5.5 as packaged in 14.04 on to 16.04.

I don't think we can treat this as a bug unless you can demonstrate a specific case that doesn't work. If you can provide a broken case, we can consider what needs doing about it then. Until then, I don't think we can expect to make any progress on a hypothetical problem.