DM-35675: Remove Gen2

[timj]

Checklist

• ran Jenkins
• added a release note for user-visible changes to doc/changes

[codecov]

Codecov Report

Merging #267 (75719fa) into main (e718c22) will increase coverage by 9.39%.
The diff coverage is 80.00%.

@@            Coverage Diff             @@
##             main     #267      +/-   ##
==========================================
+ Coverage   72.17%   81.57%   +9.39%     
==========================================
  Files          60       57       -3     
  Lines        6779     5938     -841     
  Branches     1399     1221     -178     
==========================================
- Hits         4893     4844      -49     
+ Misses       1658      868     -790     
+ Partials      228      226       -2     

Impacted Files	Coverage Δ
python/lsst/pipe/base/connections.py	72.88% <ø> (ø)
python/lsst/pipe/base/pipelineIR.py	86.26% <ø> (ø)
python/lsst/pipe/base/task.py	78.63% <ø> (ø)
python/lsst/pipe/base/argumentParser.py	76.92% <63.63%> (+74.04%)	⬆️
python/lsst/pipe/base/cmdLineTask.py	53.57% <100.00%> (+50.96%)	⬆️
python/lsst/pipe/base/__init__.py	84.61% <0.00%> (-15.39%)	⬇️

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[erykoff]

I'm not sure if the version strings for the deprecations are correct. Otherwise, an impressive score of +53 -2847!

[erykoff]

In all of these, should the version listed be v23.0 (current) or v24.0 (next), thus promising that this routine will be in v24 but once that is released can be deleted? Reading the docs is ... unclear ... but that's how I read it: https://developer.lsst.io/stack/deprecating-interfaces.html#python-deprecation

[timj]

We already promised that Gen2 was deprecated and could be removed any time as part of the v23 release. My statement is that CmdLineTask has been deprecated since v23 but now actually tells you it has been deprecated since then. I don't really see any point in keeping this code around for another two release cycles where it doesn't actually do anything and will break if something uses it. The "version" here is the version the code was formally deprecated. I have not included in the statements when we will actually delete the stubs but I was assuming I could do it as soon as nothing in lsst_distrib uses CmdLineTask.

[timj]

I talked it over with @ktlim and he thinks that saying "since v23" is fine here.