Just a few observations before release.

1) The verification for Jammy apparently has a copy-paste error,
as the banner about the env var is present (step 5) _before_ the
package from -proposed -- which adds it -- is installed (step 6).

To be clear, this is not a problem and should not block the release,
as the _new_ behavior (with -proposed installed) is what matters,
and that looks correct in the output:
- env var undefined/no opt-in = old behavior;
- env var defined/opted-in = new behavior.

The verification for Focal is OK on that regard (does not show the
banner in step 5).

2) The autopkgtests for python2.7/focal failed, but this is not due to these 
changes.
I re-run the tests with the trigger migration-reference/0, and they continue to 
fail.

This is expected, since the changes are opt-in / are not enabled by default.
The only change which _is_ enabled by default is the new banner during build,
but that output is likely not checked for, I'd imagine (ie, it's OK to change).

3) There's been a recent rebuild of the autopkgtest database, and I'd have to
verify the status (ie, finished?) and impact (eg, report pages) at the moment
to make sure this is OK on that regard.

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Touch seeded packages, which is subscribed to python2.7 in Ubuntu.
https://bugs.launchpad.net/bugs/2002043

Title:
  Python extension modules get built using wrong compiler flags with
  python2

Status in python2.7 package in Ubuntu:
  Invalid
Status in python2.7 source package in Bionic:
  Won't Fix
Status in python2.7 source package in Focal:
  Fix Committed
Status in python2.7 source package in Jammy:
  Fix Committed
Status in python2.7 source package in Kinetic:
  Invalid
Status in python2.7 source package in Lunar:
  Invalid
Status in python2.7 source package in Mantic:
  Invalid

Bug description:
  [ Impact ]

  When compiling Python extensions using Python2, CFLAGS optimization
  flags are dropped.

  This behavior has been caused by our update in this patch
  
http://archive.ubuntu.com/ubuntu/pool/universe/p/python2.7/python2.7_2.7.18-1~20.04.3.diff.gz
  which differs from upstream.

  The fix modifies the portion of code in Lib/distutils/sysconfig.py
  which gets the cflags from the environments, and includes the dropped
  OPT flag from get_config_vars().

  [ Test Plan ]

  There will be 2 separate tests for this bug:
  * Ensuring no-change rebuilds are not changed
  * Ensuring local builds are not changed unless environment variable is set

  Test 1) No-change rebuilds

  To test that no-change rebuilds are not changed, the package python-
  stdlib-extensions will be built against the new python2.7, and confirm
  the compiler flags are not altered. This will be a manual test and
  visual inspection of the build logs.

  Test 2) Functional test

  1. Create test container
  $ lxc launch ubuntu:jammy jammy-2002043
  $ lxc shell jammy-2002043

  2. Install required packages
  For Jammy
  # apt update -y && apt install -y python2 python-pip
  For Focal
  # apt update -y && apt install -y python2 python-setuptools gcc

  3. Create test files
  # mkdir testprog
  # cd testprog
  # cat >setup.py <<EOL
  from setuptools import setup, Extension

  setup(
      name="test",
      ext_modules=[Extension("test", sources=["testmodule.c"])],
      zip_safe=False
  )
  EOL
  # cat >testmodule.c <<EOL
  #include <stdio.h>

  int main(void)
  {
          printf("This is test program");
          return 0;
  }
  EOL

  4. Compile a test program
  # python2 setup.py build_ext --inplace

  5. Check CFLAGS
  # python2 -c "import sysconfig; print(sysconfig.get_config_var('CFLAGS'))"
  -fno-strict-aliasing -DNDEBUG -g -fwrapv -O2 -Wall -Wstrict-prototypes 
-Wdate-time -D_FORTIFY_SOURCE=2 -g 
-ffile-prefix-map=/build/python2.7-W40Ff2/python2.7-2.7.18=. -flto=auto 
-ffat-lto-objects -flto=auto -ffat-lto-objects -fstack-protector-strong 
-Wformat -Werror=format-security

  6. Check the flags used to compile the test wheel
  # strings build/lib.linux-x86_64-2.7/test.so  | grep -- -O
  GNU GIMPLE 11.4.0 -mtune=generic -march=x86-64 -g -g -g -g -O2 -fno-openmp 
-fno-openacc -fcf-protection=full -fno-strict-aliasing -fwrapv 
-fstack-protector-strong -ffat-lto-objects -fstack-protector-strong -fPIC 
-fltrans

  7. Install fixed python
  Once updated, this will simply be an apt update && apt upgrade
  # add-apt-repository ppa:mitchdz/python2.7-optimization-flags -y
  # apt install -y python2.7
  # dpkg -s python2.7 | grep Version:
  Version: 2.7.18-13ubuntu1.2~jammy9

  8. Clean build
  # rm -rf build/ test.so

  9. Enable opt-in environment variable
  # export APPLY_LP2002043_UBUNTU_CFLAGS_WORKAROUND=""

  9. Rebuild with new python2.7 installed
  # python2 setup.py build_ext --inplace

  10. Check build flags
  # strings build/lib.linux-x86_64-2.7/test.so  | grep -- -O
  GNU GIMPLE 11.4.0 -mtune=generic -march=x86-64 -g -g -g -g -O2 -O2 
-fno-openmp -fno-openacc -fcf-protection=full -fno-strict-aliasing -fwrapv 
-fstack-protector-strong -ffat-lto-objects -fstack-protector-strong -fPIC 
-fltrans
  GNU C17 11.4.0 -mtune=generic -march=x86-64 -g -g -O2 -fno-strict-aliasing 
-fwrapv -flto -flto -ffat-lto-objects -fstack-protector-strong -fPIC 
-fasynchronous-unwind-tables -fstack-protector-strong -fstack-clash-protection 
-fcf-protection

  [ Where problems could occur ]

  * Changing optimization flags can cause a myriad of unattended side effects, 
but the change being opt-in means the users should be aware a change is being 
made
  * The change is opt-in, so an informative message is printed to the console 
to spread awareness of the issue and how to use the workaround. A questionably 
made CI/CD system might see the new console output and flag it as a failure, so 
it is important to choose wording carefully.

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