AppTools 5.2.0

This is a minor release, focusing primarily on Python 3.8 support and updating of development workflows.

Thanks to the following contributors:

• Aaron Ayres
• Mark Dickinson
• Jonas Heinrich
• Robert T. McGibbon
• Sai Rahul Poruri
• Corran Webster

Features

• Replace some uses of on_trait_change and depends_on with observe.
  (#285, #289)
• Use importlib.resources in preference to importlib_resources
  on new enough Python versions. (#284)

Fixes

• Replace eval with ast.literal_eval in apptools.preferences.
  (#299)
• Use context managers to handle locks in apptools.preferences. (#306)
• Fix test failures due to collections.abc changes in Python 3.10. (#313)
• Remove a redundant elif branch in preference_binding. (#298)

Documentation

• Copyrights have been updated for 2022. (#307)
• A Read the Docs configuration file has been added. (#296)
• A use of the deprecated contributes_to decorator in the documentation
  has been fixed. (#286)

Build

• The default branch has been renamed from master to main. (#297)
• etstool.py now supports Python 3.8 as well as Python 3.6, and test
  workflows will run on both Python 3.6 and Python 3.8. (#316)
• Continuous integration now uses GitHub Actions instead of Travis CI
  and Appveyor. (#288, #291, #292)
• Added a GitHub Actions test workflow that tests against PyPI packages instead
  of EDM packages. (#314)
• Added a GitHub Actions workflow to automatically publish releases to PyPI.
  (#315)
• Cron job failures are now reported to the main ETS Slack channel, not the
  bots channel. (#295, #308)
• The cron job can now also be triggered manually. (#294)