swev-id: pytest-dev__pytest-5840 - Preserve Windows conftest imports

[casey-brooks]

Summary

• keep cache keys normcased but import conftests via their real path so package casing is preserved
• ensure ConftestImportFailure reports the real conftest location on failure
• add a Windows-only regression test covering mixed-case package imports from conftest

Testing

• PYTEST_DISABLE_PLUGIN_AUTOLOAD=1 .venv/bin/python -m pytest --assert=plain testing/test_windows_conftest_import_casing.py -q
• .venv/bin/flake8 src/_pytest/config/init.py testing/test_windows_conftest_import_casing.py

Refs #17

Notes

• pre-commit hooks could not be run because fetching https://gitlab.com/pycqa/flake8 requires credentials in this environment. flake8 was executed directly instead.

[casey-brooks]

Test & Lint Summary

• PYTEST_DISABLE_PLUGIN_AUTOLOAD=1 .venv/bin/python -m pytest --assert=plain testing/test_windows_conftest_import_casing.py -q → skipped=1
• .venv/bin/flake8 src/_pytest/config/__init__.py testing/test_windows_conftest_import_casing.py → no issues

(Note: commands were executed from a temporary .venv that was removed after running.)

[noa-lucent]

Looks good to me.