Release Checklist

Main Release

Released quarterly on January 2nd, April 1st, July 1st and October 15th.

Open a release ticket e.g. https://github.com/python-pillow/Pillow/issues/3154
Develop and prepare release in master branch.
Check GitHub Actions, Travis CI and AppVeyor to confirm passing tests in master branch.
Check that all of the wheel builds Pillow Wheel Builder pass the tests in Travis CI.
In compliance with PEP 440, update version identifier in src/PIL/_version.py
Update CHANGES.rst.
Run pre-release check via make release-test in a freshly cloned repo.

Create branch and tag for release e.g.:

git branch 5.2.x
git tag 5.2.0
git push --all
git push --tags

Create source distributions e.g.:
```
make sdist
```
Create binary distributions
Upload all binaries and source distributions e.g. twine upload dist/Pillow-5.2.0*
Create a new release on GitHub
In compliance with PEP 440, increment and append .dev0 to version identifier in src/PIL/_version.py

Released as needed for security, installation or critical bug fixes.

Make necessary changes in master branch.
Update CHANGES.rst.
Check out release branch e.g.:
```
git checkout -t remotes/origin/5.2.x
```
Cherry pick individual commits from master branch to release branch e.g. 5.2.x.
Check GitHub Actions, Travis CI and AppVeyor to confirm passing tests in release branch e.g. 5.2.x.
In compliance with PEP 440, update version identifier in src/PIL/_version.py
Run pre-release check via make release-test.
Create tag for release e.g.:
```
git tag 5.2.1
git push
git push --tags
```
Create source distributions e.g.:
```
make sdist
```
Create binary distributions
Upload all binaries and source distributions e.g. twine upload dist/Pillow-5.2.1*
Create a new release on GitHub

Released as needed privately to individual vendors for critical security-related bug fixes.

Prepare patch for all versions that will get a fix. Test against local installations.
Commit against master, cherry pick to affected release branches.
Run local test matrix on each release & Python version.
Privately send to distros.
Run pre-release check via make release-test
Amend any commits with the CVE #

On release date, tag and push to GitHub.

git checkout 2.5.x
git tag 2.5.3
git push origin 2.5.x
git push origin --tags

Contact @cgohlke for Windows binaries via release ticket e.g. https://github.com/python-pillow/Pillow/issues/1174.
Download and extract tarball from @cgohlke and twine upload *.

git clone https://github.com/python-pillow/pillow-wheels
cd pillow-wheels
./update-pillow-tag.sh [[release tag]]

Make sure the default version for Read the Docs is up-to-date with the release changes

Update Pillow in the Docker Images repository

git clone https://github.com/python-pillow/docker-images
cd docker-images
./update-pillow-tag.sh [[release tag]]