Revision as of 19:53, 23 April 2019

Retire Python 2 (and let it all burn)

Summary

The python2 package and all its subpackages will be removed from Fedora 32. A legacy python27 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

Targeted release: Fedora 32
Last updated: 2019-04-23
Tracker bug: <will be assigned by the Wrangler>

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 python2 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 fedora-obsolete-packages.

The python27 package

Similarly to existing python36, python37 etc. packages, a python27 package will be created. This package is indented for Python developers who still need to support the legacy version of Python. This package is indented 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 dependent upon.

The python27 package has several drawbacks compared to the original python2 package:

it is "flat" - there are no subpackages, everything lives in one package
there is no debug build (previously available as python2-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 dependent 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 python27 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 chromium package, the request should contain python-psutil and other dependent packages. (Yes, this is tedious. Maintaining a Python 2 dependent package is a burden.) A Python 3 plan is a must for such an exception.

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

Proposal owners:
- retire python2
- introduce python27
- remove all python2 dependent packages that do not have FESCo exceptions
- obsolete removed packages that break the upgrade path via fedora-obsolete-packages

Other developers:
- remove their python2 dependent packages without exceptions
- get exceptions if needed
- fix broken dependencies

Release engineering: #Releng issue number (a check of an impact with Release Engineering is needed)
- List of deliverables: none

Policies and guidelines: Python 2 packaging is against the guidelines since Fedora 30. Python 2 packaging guidelines will be removed from Python Appendix.

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 python27 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.

@@ Line 17: / Line 17: @@
 We request that you maintain the same order of sections so that all of the change proposal pages are uniform.
 -->
-<!-- The actual name of your proposed change page should look something like: Changes/Your_Change_Proposal_Name.  This keeps all change proposals in the same namespace -->
 <!-- The actual name of your proposed change page should look something like: Changes/Your_Change_Proposal_Name.  This keeps all change proposals in the same namespace -->
@@ Line 27: / Line 25: @@
 Note that motivation for the change should be in the Motivation section below, and this part should answer the question "What?" rather than "Why?". -->
-The {{package|python2}} package and all it's subpackages will be removed from Fedora 32.
+The {{package|python2}} package and all its subpackages will be removed from Fedora 32.
 A legacy {{package|python27}}  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.
@@ Line 67: / Line 65: @@
 <!-- Expand on the summary, if appropriate.  A couple sentences suffices to explain the goal, but the more details you can provide the better. -->
-Python 2 is unsupported upstream since 2020-01-01. After two phased approaches to limit the dependent packages on Python 2:
+Python 2 is unsupported upstream since 2020-01-01. Packages dependent on Python 2 are being removed from Fedora for several releases already:
 * [[Changes/Mass_Python_2_Package_Removal|Fedora 30 Mass Python 2 Package Removal]]
 * [[Changes/F31_Mass_Python_2_Package_Removal|Fedora 31 Mass Python 2 Package Removal]]
-The Python maintenance team has decided to pull the plug. The {{package|python2}} package and all it' subpackages will be retired (read: removed) from Fedora 32 (Rawhide) as soon as Fedora 31 is branched.
+Now, the Python maintainers have decided to pull the plug. The {{package|python2}} 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 week before the planned Fedora 32 Mass Rebuild.
+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,
@@ Line 81: / Line 79: @@
 The rules also apply to modules built for Fedora 32+.
-The packages removal will be executed in an automated fashion.
+The package removal will be executed in an automated fashion.
-Removed packages that would otherwise block the upgrades to Fedora 32 will be obsoleted from {{package|fedora-obsolete-packages}}.
+Removed packages that would block the upgrades to Fedora 32 will be obsoleted from {{package|fedora-obsolete-packages}}.
 === The python27 package ===
@@ Line 97: / Line 95: @@
 * there is no debug build (previously available as {{package|python2-debug}})
 * there is no <code>/usr/bin/python</code> (note: there might be already the case before this change)
-* any special backwards compatible provides are removed (this package is not intended to be dependent upon)
+* any special backwards compatible Provides are removed (this package is not intended to be dependent upon)
 === FESCo exceptions ===
@@ Line 103: / Line 101: @@
 We realize that there are some packages whose removal could seriously hurt Fedora. FESCo can grant exceptions for packages to use the {{package|python27}} as a runtime or build dependency.
-The package maintainer is responsible to check the entire dependency chain and they need to request exception for the entire list of packages. For example, when seeking exception for the {{package|chromium}} package, it should contain {{package|python-psutil}} and other dependent packages. Yes, this is tedious. Maintaining a Python 2 dependent package is a burden. A Python 3 plan is a must for such exception.
+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|chromium}} package, the request should contain {{package|python-psutil}} and other dependent packages. (Yes, this is tedious. Maintaining a Python 2 dependent package is a burden.) A Python 3 plan is a must for such an exception.
 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.
+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.
@@ Line 145: / Line 143: @@
 * 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, arguably complicated but possible
+* it leaves Fedora packagers an option to keep using it (complicated, but possible)
 While:
@@ Line 151: / Line 149: @@
 * 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 much security bugs as possible, without the upstream involvement, this will not always be possible. This change moves Python 2 from second class citizen to third class citizen. Python 2 was deprecated since Fedora 30.
+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 ==
@@ Line 157: / Line 157: @@
 ** retire {{package|python2}}
 ** introduce {{package|python27}}
-** remove all {{package|python2}} dependent packages without exceptions
+** remove all {{package|python2}} dependent packages that do not have FESCo exceptions
 ** obsolete removed packages that break the upgrade path via {{package|fedora-obsolete-packages}}
 <!-- What work do the feature owners have to accomplish to complete the feature in time for release?  Is it a large change affecting many parts of the distribution or is it a very isolated change? What are those changes?-->
@@ Line 184: / Line 184: @@
 <!-- REQUIRED FOR SYSTEM WIDE CHANGES -->
-Majority of removed packages will be obsoleted and removed on upgrade.
+The majority of removed packages will be obsoleted and removed on upgrade.
-Users needing Python 2 libraries will need to use pip and virtualenv.
+Users needing Python 2 libraries will not find these packaged as RPMs. They may install upstream versions using pip and virtualenv.
 == How To Test ==
@@ Line 231: / Line 231: @@
 <!-- If you cannot complete your feature by the final development freeze, what is the backup plan?  This might be as simple as "Revert the shipped configuration".  Or it might not (e.g. rebuilding a number of dependent packages).  If you feature is not completed in time we want to assure others that other parts of Fedora will not be in jeopardy.  -->
 * Contingency mechanism:
-** In case of great madness, FESCo can issue a general exception for packages that would otherwise prevent Fedora 32 from being composed.
+** 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 the Change, or come up with another plan. (Note that in this case, current maintainers will most likely orphan many fundamental python2 packages.)
+** 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.)
 <!-- REQUIRED FOR SYSTEM WIDE CHANGES -->
 <!-- When is the last time the contingency mechanism can be put in place?  This will typically be the beta freeze. -->

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