• fix multiprocessing lock creation leak (#982, #936, #759)
  • fixes #617 which introduced this bug (v4.29.0, released 2019-01-06, undiagnosed until now) where multiple threads could concurrently create and append process locks to a global list, then try to release them without first acquiring 👿
• major test overhaul: fix, update, and speed up
• misc CI framework updates
• code linting
• minor documentation tidy