Consider dropping pbr in favor of poetry

[portante]

We see a number of deprecation warnings whenever we run our tox builds (see the copy of the pbr bug filed below). I did a fair amount of digging into this problem and would like to propose we consider moving away from pbr in favor of poetry.

The Arcalot organization is using it with a fair amount of success.

Some various references found while digging:

• "PEP 517 – A build-system independent format for source trees"
• Python Packaging Authority
• PyPA's flit project
• "How to package and deploy CLI applications with Python PyPA setuptools build"

Below is a copy of the pbr LaunchPad bug #1993830 filed:

---

When we run our tests via tox, we see the following warnings printed:

.package recreate: /var/tmp/pportant/tox/.package
.package installdeps: setuptools >= 46.1.3., wheel >= 0.34.2
/var/tmp/pportant/tox/.package/lib/python3.10/site-packages/setuptools/command/easy_install.py:156: EasyInstallDeprecationWarning: easy_install command is deprecated. Use build and pip and other standards-based tools.
  warnings.warn(
/var/tmp/pportant/tox/.package/lib/python3.10/site-packages/setuptools/command/install.py:34: SetuptoolsDeprecationWarning: setup.py install is deprecated. Use build and pip and other standards-based tools.
  warnings.warn(

We run with tox's isolated_build parameter set to True.

"James" from the Boston Python Slack workspace did some further digging and found the culprit to be how pbr works with isolated builds (if you turn off isolated builds, the warnings don't occur):

23:22 [snoopjedi@denton ~/repos/pbench-src (main *)]
$ PYTHONWARNINGS="error:setup.py" tox -e py39 agent python
Error parsing
Traceback (most recent call last):
  File "/var/tmp/snoopjedi/tox/.package/lib/python3.9/site-packages/pbr/core.py", line 111, in pbr
    attrs = util.cfg_to_args(path, dist.script_args)
  File "/var/tmp/snoopjedi/tox/.package/lib/python3.9/site-packages/pbr/util.py", line 274, in cfg_to_args
    kwargs = setup_cfg_to_setup_kwargs(config, script_args)
  File "/var/tmp/snoopjedi/tox/.package/lib/python3.9/site-packages/pbr/util.py", line 407, in setup_cfg_to_setup_kwargs
    cmd = cls(dist)
  File "/var/tmp/snoopjedi/tox/.package/lib/python3.9/site-packages/setuptools/__init__.py", line 106, in __init__
    super().__init__(dist)
  File "/var/tmp/snoopjedi/tox/.package/lib/python3.9/site-packages/setuptools/_distutils/cmd.py", line 62, in __init__
    self.initialize_options()
  File "/var/tmp/snoopjedi/tox/.package/lib/python3.9/site-packages/setuptools/command/install.py", line 34, in initialize_options
    warnings.warn(
setuptools._deprecation_warning.SetuptoolsDeprecationWarning: setup.py install is deprecated. Use build and pip and other standards-based tools.
error in setup command: Error parsing /home/snoopjedi/repos/pbench-src/setup.cfg: SetuptoolsDeprecationWarning: setup.py install is deprecated. Use build and pip and other standards-based tools.

[SnoopJ]

I would recommend thinking about splitting this issue in half, into a "remove pbr" half and an "adopt poetry" half. I did not dig deep into pbench during our conversation, but I didn't see anything that made me think setuptools is incapable of building the project. You may still want to switch to poetry for other reasons, though