Native test suite fails on Windows because path assertion ignores repr escaping

Affected version and environment

• lark-oapi 1.7.3
• Default branch commit: 0b9e6e48b74bb4b34462fc67b7e738b27e73e697
• Windows 11
• Python 3.13.13 and 3.14.4

Problem

The repository's native pytest run has one deterministic Windows-only failure:

FAILED lark_oapi/channel/tests/test_upload_error_propagation.py::
test_gather_buffer_missing_local_file_raises_upload_failed

assert nonexistent in str(err)

gather_buffer() intentionally formats the path with {source.path!r}. On Windows, repr() doubles backslashes, so the raw nonexistent string is not a substring of the rendered exception even though the correct path is preserved in err.context["path"] and as the OSError cause.

Reproduction

From a Windows checkout with test extras installed:

python -m pytest -q -p no:cacheprovider

Observed on both tested interpreters:

• Python 3.13.13: 657 passed, 1 failed
• Python 3.14.4: 657 passed, 1 failed

The failure is at lark_oapi/channel/tests/test_upload_error_propagation.py:37; the formatting under test is at lark_oapi/channel/outbound/media/uploader.py:163.

A minimal equivalent is:

path = r"C:\tmp\does_not_exist.png"
message = f"could not read local file {path!r}"
assert path in message  # fails because message contains escaped backslashes

Expected behavior

The native test suite should pass on a supported Windows/Python environment while still checking the useful diagnostic contract.

Suggested fix

Make the assertion representation-aware (for example, assert repr(nonexistent) in the message) and retain the existing exact context assertion, which already proves that callers receive the original path value.

I searched open and closed issues, all pull request states, and repository history for the test name, upload failed, Windows path escaping, and does_not_exist.png. I found no existing report or competing fix; the old Windows path issue #1 and PR #2 concern API URL joining, not exception-message representation.

Start with lark_oapi/channel/tests/test_upload_error_propagation.py:37 and compare the assertion with the formatting at lark_oapi/channel/outbound/media/uploader.py:163. Run python -m pytest -q -p no:cacheprovider in a supported Windows environment; done means the native suite passes while the existing context-path assertion remains intact.