v267

• Deprecated using Pipenv without a lockfile (Pipfile.lock). (#1695)
• Fixed Poetry venv creation when using an outdated Python version whose ensurepip module doesn't enable isolated mode, and the app's build directory contents shadows a package imported by pip (such as brotli). (#1698)

v266

• Added a warning when the files for multiple package managers are found. In the future this warning will become an error. (#1692)
• Updated the build log message shown when installing dependencies to include the package manager command being run. (#1689)
• Changed test dependency installation on Heroku CI to now install requirements.txt and requirements-test.txt in a single pip install invocation rather than separately. This allows pip's resolver to resolve any version conflicts between the two files. (#1689)
• Improved the error messages and buildpack metrics for package manager related failures. (#1689)
• Improved the build log output, error messages and buildpack failure metrics for the NLTK downloader feature. (#1690)

v265

• Fixed Poetry installation when using outdated patch versions of Python 3.8, 3.9 and 3.10, whose bundled pip doesn't support the --python option. (#1687)

v264

• Added support for the package manager Poetry. Apps must have a pyproject.toml + poetry.lock and no other package manager files (otherwise pip/Pipenv will take precedence for backwards compatibility). (#1682)

v263

• Fixed cache handling so that it now also discards the cache when the package manager (or its version) changes. (#1679)
• Improved the build log output shown when restoring or discarding the cache. For example, if the cache was invalidated all reasons are now shown. (#1679)
• Stopped performing unnecessary cache file copies when the cache is due to be invalidated. This required moving the cache restoration step to after the bin/pre_compile hook runs. (#1679)
• Fixed cache restoration in the case where an app's requirements.txt was formerly a symlink. (#1679)
• Added buildpack metrics for the status of the cache and duration of cache restoration/saving. (#1679)

v262

• Updated buildpack-generated warning messages to use colour and be more consistently formatted. (#1666)
• Improved build log output and error messages for the bin/pre_compile and bin/post_compile customisation hooks. (#1667)

v261

• Added support for configuring the Python version using a .python-version file. Both the 3.N and 3.N.N version forms are supported (the former is recommended). The existing runtime.txt file will take precedence if both files are found, however, we recommend switching to .python-version since it is more commonly supported in the Python ecosystem. (#1664)
• Added support for specifying only the Python major version in runtime.txt instead of requiring the full Python version (for example python-3.N instead of python-3.N.N). (#1664)

v260

• Added support for Python 3.13. (#1661)
• Removed the idle3 and pydoc3 scripts since they do not work with relocated Python and so have been broken for some time. Invoke them via their modules instead (e.g. python -m pydoc). (#1661)