Scenario Context objects do not explicitly clean up the temporary directory used for containers and storages

[tonyandrewmeyer]

The Scenario Context leaves behind a temporary directory:

>>> import os
>>> import ops
>>> from ops import testing
>>> t = os.listdir("/tmp")
>>> ctx = testing.Context(ops.CharmBase, meta={"name": "test"})
>>> _ = ctx.run(ctx.on.start(), testing.State())
>>> set(os.listdir("/tmp")) - set(t)
{'tmpcd0o54a7'}
>>> os.listdir('/tmp/tmpcd0o54a7')
[]

This is the Context._tmp directory. It's used for the container root and storage root (which also means that it's shared across run calls with the same Context, which is probably not desirable but perhaps is now baked in and not changeable?), so it's available outside of the run or context manager use.

Note that the directory doesn't exist when the process exits because Python cleans it up (emitting a ResourceWarning):

$ python3 -W error -c 'import tempfile;t=tempfile.TemporaryDirectory()'
Traceback (most recent call last):
  File "/usr/lib/python3.12/weakref.py", line 666, in _exitfunc
    f()
  File "/usr/lib/python3.12/weakref.py", line 590, in __call__
    return info.func(*info.args, **(info.kwargs or {}))
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/tempfile.py", line 1075, in _cleanup
    _warnings.warn(warn_message, ResourceWarning)
ResourceWarning: Implicitly cleaning up <TemporaryDirectory '/tmp/tmp83ywjo1j'>