[BPO] dh-python 5.20220403 to focal

[Unit 193]

[Impact]

 * This is needed to refresh the yt-dlp package as it has support for 'environment markers'
 * This version could also be useful for other projects as it adds support for pyproject.

[Scope]

Backport from:
 * To me it makes sense to backport from jammy (LTS), though the version currently is the same as devel.

Backport to:
 * focal

[Other Info]

 * I have created a test backport in ppa:unit193/staging and have already utilized.

[Testing]

* focal:
[x] Package builds without modification
[x] dh-python installs cleanly and runs
[?] pybuild-plugin-pyproject installs cleanly and runs

[Dan Streetman (ddstreet)]

Comments:

1. This adds Suggests: flit, python3-build, python3-tomli, python3-installer; however, those aren't available in focal.

2. Similiarly, the newly-added package pybuild-plugin-pyproject Depends: on the python3-{build,installer,tomli} packages, which aren't available in focal.

3. This adds Breaks: and Replaces: for python2 (<< 2.7.18-2), but in focal python2 is 2.7.17-2ubuntu4. Either dh_python2 needs to be moved from python-defaults in focal (or more likely focal-backports) to this package, or this backport needs to leave out dh_python2 (and it should be verified that the only reason for the Breaks: is because of moving the dh_python2 script between packages).

There may be more issues, I didn't look in depth at all the code changes; I can do a closer review if the above issues are addressed first, or at least looked at to see if those issues are possible/reasonable to fix.

[Unit 193 (unit193)]

Sounds to me like this should just be withdrawn then. I'd only tested the python3 aspect with the removal of a lot of python2 packages from future releases.

[Thomas Ward (teward)]

Marking this as Won't Fix because of identified issues and Unit indicating that this should be withdrawn.