From Fedora Project Wiki


Retire Python 2

Summary

The Package-x-generic-16.pngpython2 package and all its subpackages will be removed from Fedora 32. A legacy Package-x-generic-16.pngpython27 package for developers and users will be provided. All packages in Fedora that need Python 2 to run will be removed from Fedora 32 regardless of their dependencies. All packages in Fedora that need Python 2 to build will be removed from Fedora 32 regardless of their dependencies. Exceptions can be granted by FESCo.

Owner

  • Name: Miro Hrončok
  • Email: <mhroncok@redhat.com> <python-devel@lists.fedoraproject.org>
  • Release notes owner:

Current status

Detailed Description

Python 2 is unsupported upstream since 2020-01-01. Packages dependent on Python 2 are being removed from Fedora for several releases already:

Now, the Python maintainers have decided to pull the plug. The Package-x-generic-16.pngpython2 package and all its subpackages will be retired (read: removed) from Fedora 32 (Rawhide) as soon as Fedora 31 is branched.

All packages depending on any python2 package will be removed. The removal starts 2 weeks before the planned Fedora 32 Mass Rebuild. Broken dependencies will not stop the removals. Packages that Fail to Build From Source and prevent to remove Python 2 subpackages may end up with broken dependencies, in cases where it is not desired, those packages will be retired instead.

The rules also apply to modules built for Fedora 32+.

The package removal will be executed in an automated fashion.

Removed packages that would block the upgrades to Fedora 32 will be obsoleted from Package-x-generic-16.pngfedora-obsolete-packages.

The python27 package

Similarly to existing Package-x-generic-16.pngpython36, Package-x-generic-16.pngpython37 etc. packages, a Package-x-generic-16.pngpython27 package will be created. This package is intended for Python developers who still need to support the legacy version of Python. This package is intended for users, who still need to use some software depending on the legacy version of Python. This package is not intended for other Fedora packages to be depended upon.

The Package-x-generic-16.pngpython27 package has several drawbacks compared to the original Package-x-generic-16.pngpython2 package:

  • it is "flat" - there are no subpackages, everything lives in one package
  • there is no debug build (previously available as Package-x-generic-16.pngpython2-debug)
  • there is no /usr/bin/python (note: there might be already the case before this change)
  • any special backwards compatible Provides are removed (this package is not intended to be depended upon)

FESCo exceptions

We realize that there are some packages whose removal could seriously hurt Fedora. FESCo can grant exceptions for packages to use the Package-x-generic-16.pngpython27 as a runtime or build dependency.

The package maintainer is responsible to check the entire dependency chain and they need to request exceptions for the entire list of packages. For example, when seeking exception for the Package-x-generic-16.pngchromium package, the request should contain Package-x-generic-16.pngpython-psutil and other dependent packages. (Yes, this is tedious. Maintaining a Python 2 dependent package is a burden.)

The exception request must include a plan for migrating to Python 3.

Any non-essential dependency must be dropped. That includes optional dependencies, test dependencies, optional subpackages etc.

Package that fail to get an exception when the removal starts (see above) will be removed. Their importance for Fedora Release Engineering, Fedora Infrastructure or any other body will not be automagically respected; every package that needs Python 2 needs an exception.

The change owners will send regular reminders to the package owners.

Benefit to Fedora

Python 2 is past upstream End of Life since 2020-01-01. This changes is generally crafted in a way that:

  • it leaves Python developers an option to use it in case they still need to support it
  • it leaves Fedora users an option to use it in case they still need it to run their (3rd party) software
  • it leaves Fedora packagers an option to keep using it (complicated, but possible)

While:

  • it removes Python 2 software from Fedora that was only preserved so far by inaction

Using Python 2 is dangerous. While the Fedora Python maintainers will try to fix as many security bugs as possible, without the upstream involvement this will be hard.

Python 2 is deprecated since Fedora 30. This change moves Python 2 from second class citizen to third class citizen.

Scope

  • Other developers:
    • remove their Package-x-generic-16.pngpython2 dependent packages without exceptions
    • get exceptions if needed
    • fix broken dependencies
  • Policies and guidelines: Python 2 packaging is against the guidelines since Fedora 30. Python 2 packaging guidelines will be removed from Python Appendix (unless the FPC wants to keep them around until F31 EOL).
  • Trademark approval: not needed for this Change

Upgrade/compatibility impact

The majority of removed packages will be obsoleted and removed on upgrade.

Users needing Python 2 libraries will not find these packaged as RPMs. They may install upstream versions using pip and virtualenv.

How To Test

Try to update Fedora 30 or 31 to 32. No python2 packages should block the upgrade. Try to run Python 2 software via the Package-x-generic-16.pngpython27 package.

User Experience

There will be close to zero Python 2 RPMs in Fedora repos. Users are encouraged to switch to Python 3 and/or use Python 2 virtual environments and pip for development.

Dependencies

Ideally, all programs that use python2 would be switched to use python3. Although we don't expect everything to be switched over, as much as possible should be, so that the ripped remaining python2 set is small as possible.

Contingency Plan

  • Contingency mechanism:
    • In case of serious issues, FESCo can issue a general exception for packages that would otherwise prevent Fedora 32 from being composed.
    • If someone steps up to maintain Python 2 (including the full ecosystem of packages now in Fedora), they can decide to discontinue removing packages, revert this Change, or come up with another plan. (Note that in this case, current maintainers will most likely orphan many fundamental python2 packages.)
  • Contingency deadline: Fedora 32 Beta
  • Blocks release? in theory it should not, in practice, it may break the release and hence it will block it until fixed
  • Blocks product? all of them?

Documentation

This page should serve as the documentation.

Release Notes

TBD.