Envisage 6.1.0

This is a minor feature release whose main focus is on compatibility with
Python 3.8 and PySide 6. It includes a collection of other cleanups and minor
fixes.

In this release, there are some changes in the way that the Envisage
Application interacts with ETSConfig. You should double check that
the locations of user data, preferences and application home directories are
the ones that you expect after upgrading.

Please note that the IPython-related portions of Envisage are currently not
compatible with the latest versions of ipykernel and IPython available from
PyPI. This has been made explicit in this release in the form of version
restrictions on those packages in the envisage[ipython] install target.

Thanks to:

• Aaron Ayres
• Mark Dickinson
• Sai Rahul Poruri
• Corran Webster

Changes

• The Application.user_data directory no longer includes the id
  of the application, but instead matches the ETSConfig.user_data. (#467)
• The Envisage Application will no longer try to change the
  ETSConfig.application_home attribute. (#467)
• The PackageResourceProtocol now uses importlib.resources instead
  of pkg_resources. (#466)
• The IPython-related features of Envisage require ipykernel version < 6 and
  IPython version < 8. (#449)

Fixes

• Fix EggPluginManager to use current pkg_resources.working_set. (#444)

Refactoring and maintenance

• Simplify ImportManager by using importlib. (#465)
• Update end year in copyright headers. (#458)

Tests

• The tests no longer rely on pre-built eggs for test packages. (#459, #436)
• Skip tests for recent ipykernel, and add check for IPython version. (#457)
• Work around a Python 3.6 issue with isinstance and lru caches in tests.
  (#470)
• Fix an EggBasketPluginManager test that only passed due to test
  interactions. (#443)
• Some pickles used in testing have been regenerated in order to work
  correctly with more recent versions of Traits. (#472)
• Fix poorly specified action and menu groups in tests. (#468)
• Fix test hangs with PySide2 / macOS 11. (#454)
• Skip an ipykernel-using test if ipykernel is not available in the test
  environment. (#423)

Examples

• Fixes for the Attractors example. (#408, #416)

Documentation

• Code samples in the documentation now have a "copy" button. (#474)
• Stylistic changes and updates to documentation. (#406)
• Fix documentation links to examples on main branch. (#447)
• Add a Read the Docs config file. (#434)
• Miscellaneous minor fixes. (#435)

Build and CI

• Update build machinery to support Python 3.8 and PySide 6. (#477)
• Add workflow to automatically upload releases to PyPI. (#478)
• Set up Slack notification for cron jobs. (#433)
• Cron job failures are now reported to the main Slack channel, not
  to the bots channel. (#473)
• Add GitHub Actions workflow to test PyPI install. (#450)
• The default branch has been renamed from master to main. (#446)
• Update classifiers for Python 3.10. (#437)
• Port CI from Appveyor to GitHub Actions. (#432, #426)
• Simplify flake8 command in etstool.py. (#431)
• Traits version 6.2 or later is now required. (#410)