Not sure if this has happened before or is due to a new test, but there were recently 2 different AppVeyor PR builds that got stuck and then only aborted due to the 3 hour timeout.

I first saw it in this PR build of PR 7013 and then also in this PR build of PR 7033
The log stops at different tests in those 2 runs, therefore not sure if it is a problem of a specific test or aftereffect of a certain test suite or an AppVeyor problem