Version 1.0.0 fails on Python 3.8 with: TypeError: 'type' object is not subscriptable

[andy-maier]

PR #297 fixed my earlier problem on Python 3.8, but it did that by just adding Python 3.8 as a supported version to package versions 0.32.2 and later.

When using the latest version 1.0.0 on Python 3.8, we encountered the following error:

$ python3 -m bumpversion bump --new-version 25.3.3-a262.dev6 patch --no-tag --no-commit --allow-dirty --verbose
Traceback (most recent call last):
  File "/usr/lib/python3.8/runpy.py", line 194, in _run_module_as_main
    return _run_code(code, main_globals, None,
  File "/usr/lib/python3.8/runpy.py", line 87, in _run_code
    exec(code, run_globals)
  File "/home/jenkins/.local/lib/python3.8/site-packages/bumpversion/__main__.py", line 3, in <module>
    from bumpversion.cli import cli
  File "/home/jenkins/.local/lib/python3.8/site-packages/bumpversion/cli.py", line 12, in <module>
    from bumpversion.bump import do_bump
  File "/home/jenkins/.local/lib/python3.8/site-packages/bumpversion/bump.py", line 6, in <module>
    from bumpversion.hooks import run_post_commit_hooks, run_pre_commit_hooks, run_setup_hooks
  File "/home/jenkins/.local/lib/python3.8/site-packages/bumpversion/hooks.py", line 8, in <module>
    from bumpversion.config.models import Config
  File "/home/jenkins/.local/lib/python3.8/site-packages/bumpversion/config/__init__.py", line 7, in <module>
    from bumpversion.config.files import get_pep621_info, read_config_file
  File "/home/jenkins/.local/lib/python3.8/site-packages/bumpversion/config/files.py", line 9, in <module>
    from bumpversion.config.models import PEP621Info
  File "/home/jenkins/.local/lib/python3.8/site-packages/bumpversion/config/models.py", line 14, in <module>
    from bumpversion.scm.models import SCMInfo  # NOQA: TC001
  File "/home/jenkins/.local/lib/python3.8/site-packages/bumpversion/scm/models.py", line 18, in <module>
    class SCMConfig:
  File "/home/jenkins/.local/lib/python3.8/site-packages/bumpversion/scm/models.py", line 30, in SCMConfig
    moveable_tags: list[str] = field(default_factory=list)
TypeError: 'type' object is not subscriptable

This happened in a Jenkins environment, and I was not able to reproduce it locally. But the source code location that failed at the bottom end of the traceback uses a construct that was introduced only in Python 3.9, according to https://stackoverflow.com/a/75202688/1424462 and https://docs.python.org/3.9/whatsnew/3.9.html#type-hinting-generics-in-standard-collections.

We are currently circumventing the issue by pinning bump-my-version to 0.29.0 on Python 3.8.

I'm afraid I have to pull up my earlier suggestion again to yank the older versions that claim Python 3.8 support but don't work there.

[coordt]

This is so frustrating that the 3.8 tests pass with this obvious issue. Fix coming.