sage_bootstrap: Remove purported Python 2.6 support

[vbraun]

• Apparently sage-bootstrap-python using python 2.6 is broken already - ​https://groups.google.com/g/sage-support/c/GniJKQ0MaMY/m/DugFUprJAwAJ
• Platforms such as RHEL 6 and Centos 6 reached their EOL at the end of 2020; and Docker-based testing of centos-6 no longer works

In this ticket, we

• delete sage_bootstrap/compat/argparse.py
• Change ​​http://doc.sagemath.org/html/en/developer/packaging.html#checksums and any other related documentation (last modified in #31192)

This is on top of #31419 so that we have to change README only once.

[karandesai-96]

I changed the directory to SAGE_ROOT/build/sage_bootstrap and checked out contents : ` . ├── cksum.py ├── cmdline.py ├── compat.py ├── config.py ├── download.py ├── env.py ├── init.py ├── levenshtein.py ├── logger.py ├── mirror_list.py ├── package.py ├── README ├── stdio.py ├── tarball.py └── updater.py

`

There is no subdirectory named "compat".

[embray]

This can also help with #9536 since Python 2.7+ supports the --no-user-cfg option to setup.py/setup.cfg, which Python 2.6 does not (just thought of this since it's an issue I looked at recently).

[slelievre]

See #28000 for complete removal of Python 2 support.

[embray]

I'm pretty sure Python 2.6 support is completely removed from sagelib itself, just not from sage_bootstrap.

[dimpase]

should we clean up sage_bootstrap in this respect here? (this would mean to require system's Python 2.7 or better for building)

[slelievre]

Removing the ability to bootstrap from Python 2.6 probably does not need to happen before we remove Python 2 support in sagelib.

[dimpase]

From the brief look at the code, this is a change that may be done now, and after all noone must Python 2.6 now.

[fbissey]

It's the default python on redhat/centos 6 and possibly some ancient debian. I'll note that redhat/centos 6 have access to newer python but someone with admin privileges and knowledge of software collections is needed.

[dimpase]

I'll make an experimental branch to remove vendored argparse

[dimpase]

New commits:

​2d0891d

remove vendored argparse

[dimpase]

tests run on ​https://github.com/dimpase/sage/pull/11

[mkoeppe]

Also need to update build/tox.ini

[git]

Branch pushed to git repo; I updated commit sha1. New commits:

​f734c8e

remove py26 from tox

[mkoeppe]

sage-system-python should probably check that python is new enough.

[mkoeppe]

New commits:

​1d36a2e	build/bin/sage-system-python: Try python first
​890ef67	Merge branch 't/29890/build_bin_sage_system_python__try__python__first' into t/20023/build/unvendorargparse
​5ff700a	build/bin/sage-system-python: Test that python has argparse

[mkoeppe]

I set it to sage-pending because I think 9.2 may be too early to merge this ticket.

[dimpase]

needs a rebase - set milestone to 9.3

[dimpase]

it seems that the branch ought to remove build/sage_bootstrap/compat, no?

[mkoeppe]

I think sage 9.3 is still too early for removing the support for building the distribution on systems that only have python 2.6. Setting the milestone back to pending

[git]

Branch pushed to git repo; I updated commit sha1. This was a forced push. New commits:

​5946eb4	remove vendored argparse
​5500d19	remove py26 from tox
​0f3d369	build/bin/sage-bootstrap-python: Test that python has argparse

[git]

Branch pushed to git repo; I updated commit sha1. New commits:

​86c05e6

src/doc/en/installation/source.rst: sage-bootstrap-python cannot be 2.6

[git]

Branch pushed to git repo; I updated commit sha1. New commits:

​5e810dd	build/pkgs/python3: Update to 3.9.2
​60d6433	Merge #31419
​06873c2	README.md: Update Python requirement for build

[dimpase]

should we also remove py33 from build/tox.ini ?

[git]

Branch pushed to git repo; I updated commit sha1. New commits:

​c948b02

build/tox.ini: Remove py33, add py39, py310

[dimpase]

OK, this works

[mkoeppe]

Thanks.

[vbraun]

Merge conflict

[git]

Branch pushed to git repo; I updated commit sha1. New commits:

​92533b8	Merge tag '9.3.beta8' into t/20023/build/unvendorargparse
​0cac965	build/pkgs/ecl: Update to 21.2.1, remove patches included in new version
​6a62484	delete all merged upstream patches: MR 210, MR 231
​b1fe929	Merge #31336

[git]

Branch pushed to git repo; I updated commit sha1. This was a forced push. New commits:

​6ef52d6	build/pkgs/python3/spkg-configure.m4: Issue a deprecation warning for system python 3.6
​cf55561	Merge branch 't/31192/installation_manual__fix_documentation_of_python_prerequisite__sage_bootstrap_python_' into t/31318/python3_spkg_configure_m4__add_deprecation_warning_regarding_system_python_3_6
​0fb8646	README.md, src/doc/en/installation/source.rst: Mention/update version range for python3
​8cd0bcc	Merge #31318