Zope-4-Welcome-Sprint in Halle, Germany; May 16th to 18th, 2018

One to solve before the sprint if possible, is this one:

This is the problem causing our jenkins builds to hang some times.
See:

and

It can also be reproduced outside of running tests. Sometimes when stopping Zope, it will end with a keyerror instead of closing down nicely. This can probably cause issues with proper reporting of shutdown (docker etc.)