Hello,
Today I have migrated the Wikimedia Jenkins tox jobs suffixed with -jessie to a new infrastructure. That impacts pywikibot/core and pywikibot/wikibase among others.
In short, the new infrastructure is a pool of Debian Jessie VMs that are discard once a job has completed. It offers your jobs a guaranteed fresh environment and let us tune the pool to scale the infra. Later, we will be able to remove the whitelist and have tests run for anyone proposing a patch.
I will monitor the jobs over the week-end. In case of weird issue please fill a task to Phabricator against #continuous-integration-scaling and send me a private email :-)
Happy hacking week-end!