Release 1.4.0

[bgilbert]

OpenSlide Python release process

• Update CHANGELOG.md and version in openslide/_version.py
• Create and push signed tag
• Find the workflow run for the tag
  • Once the build finishes, approve deployment to PyPI
  • Download the docs artifact
• Verify that the workflow created a PyPI release with a description, source tarball, and wheels
• Verify that the workflow created a GitHub release with release notes, a source tarball, and wheels
• cd into website checkout; rm -r api/python && unzip /path/to/downloaded/openslide-python-docs.zip && mv openslide-python-docs-* api/python
• Update website: _data/releases.yaml, _includes/news.md
• Start a CI build of the demo site
• Update Ubuntu PPA
• Update Fedora and EPEL packages
• Check that Copr package built successfully
• Send mail to -announce and -users
• Post to forum.image.sc
• Update MacPorts package

[bgilbert]

Automatic creation of the GitHub release failed due to #301, so I've created the release manually from the GitHub Actions run artifacts.

[bgilbert]

Skipping EPEL update because the changes relevant to EPEL aren't worth the churn per the EPEL update policy.

[bgilbert]

It's no longer feasible to keep the EPEL 8 package building on the system Python, which is 3.6 and thus unsupported. The EPEL 8 Copr will stay at OpenSlide Python 1.3.1.

[bgilbert]

Distro packages on older distros need #306. Closing in favor of #307.