The patchtest test-suite is currently running on pyhton2 and a migration to python3 should be done in the following milestones.
As bug 10803, the migration is not urgent at this point; the main focus right now is stabilization and new patch checks. Moving this into the next release.
The test suite migration is done, but some tests must be completed on the virtual machine before closing this bug.
master-next has the current implementation. Although not yet in master, this work is completed.