OutputStreamAthenaPool + PrimaryDPDMaker + LongLivedParticleDPDMaker: Python3 fixes, see ATLASRECTS-5598
This along w/ @rbielski's Trigger API fix in !34986 (merged) should fix ATLASRECTS-5598. We need this to go in as soon as possible so that we can recover some of the SPOT test jobs.