## heroku/ruby

### Changed

- Default process types defined by the Ruby buildpack now use IPv6 host `::` which is equivalent of IPv4 host `0.0.0.0`. This will only affect applications that do not define a `web` process type via the `Procfile` and [Procfile Cloud Native Buildpack](https://github.com/heroku/buildpacks-procfile). Those applications must make sure to update their configuration to bind to an IPv6 host. ([#354](heroku/buildpacks-ruby#354))

### Added

- The buildpack now warns the user when environmental variables used in running the default process are not defined. ([#307](heroku/buildpacks-ruby#307))

## heroku/ruby

### Changed

- Default process types defined by the Ruby buildpack now use IPv6 host `::` which is equivalent of IPv4 host `0.0.0.0`. This will only affect applications that do not define a `web` process type via the `Procfile` and [Procfile Cloud Native Buildpack](https://github.com/heroku/buildpacks-procfile). Those applications must make sure to update their configuration to bind to an IPv6 host. ([#354](heroku/buildpacks-ruby#354))

### Added

- The buildpack now warns the user when environmental variables used in running the default process are not defined. ([#307](heroku/buildpacks-ruby#307))

Co-authored-by: heroku-linguist[bot] <136119646+heroku-linguist[bot]@users.noreply.github.com>

## heroku/python

### Removed

- Removed support for the deprecated `runtime.txt` file. Python versions must now be specified using a `.python-version` file instead. ([#352](heroku/buildpacks-python#352))
- Removed support for Ubuntu 20.04 (and thus Heroku-20 / `heroku/builder:20`). ([#358](heroku/buildpacks-python#358))

### Changed

- Improved the error messages shown when `.python-version` contains an invalid Python version or stray invisible characters (such as ASCII control codes). ([#353](heroku/buildpacks-python#353) and [#354](heroku/buildpacks-python#354))
- Improved the error messages shown if I/O errors occur. ([#355](heroku/buildpacks-python#355) and [#356](heroku/buildpacks-python#356))