tests still failing on jenkins (but locally, too)

Unfortunately this is a ~~fuzzy~~ tedious topic

Sometimes errors are not reproduceable. It can be that a test fails and that the vagrant box is unusable afterwards, leading to a failure of subsequent tests (which would otherwise succeed). Sometimes, tests succeed when re-run or run with `keep_box=true` which might indicate that a test has to be run slower, ie one needs to hack `sleep`s in between...