Fixes warning seen during packaging operations
```
➜ mitogen git:(master) ✗ uv build --sdist
Building source distribution...
...
!!
********************************************************************************
Please consider removing the following classifiers in favor of a SPDX license expression:
License :: OSI Approved :: BSD License
See https://packaging.python.org/en/latest/guides/writing-pyproject-toml/#license for details.
********************************************************************************
!!
self._finalize_license_expression()
running egg_info
...
```
Most of the necessary changes were made in recent PEP 451 commits. This bumps
the CI jobs, and declares the support. Test dependendancies are bumped to
latest supportted/available versions.
refs #1033
* ansible: use unicode_literals everywhere since it only needs to be
compatible back to 2.6.
* compat/collections.py: delete this entirely and rip out the parts of
functools that require it.
* Introduce serializable Kwargs dict subclass that translates keys to
Unicode on instantiation.
* enable_debug_logging() must set _v/_vv globals.
* cStringIO does not exist in 3.x.
* Treat IOLogger and LogForwarder input as latin-1.
* Avoid ResourceWarnings in first stage by explicitly closing fps.
* Fix preamble_size.py syntax errors.
This eliminates the possibility of the filesystem and setup.py
diverging, as had happened with ansible_mitogen/connection/ vs
ansible_mitogen/connection.py
py_packages is not a field know by distutils or setuptools. The closest
is `py_modules`, which perhaps what the erroneus line here started as.
Fixes#43
Alex Willmer