[ENH] Improve error handling of _get_data_by_filename in data/examples.py

[victorwon2001]

LLM generated content, by GPT-5.6 Sol

Reference Issues/PRs

Fixes #2152

What does this implement/fix? Explain your changes.

Downloads for uncached example data are now written to a temporary directory under the cache location and moved to the final cache path only after urlretrieve() completes successfully. Failed transfers therefore do not leave a partial file that a later call could mistake for a valid cached download, while existing cache-hit behavior and download exceptions remain unchanged.

What should a reviewer concentrate their feedback on?

• The temporary-download publication behavior and preservation of the existing cache and exception semantics.

Did you add any tests for the change?

Yes. Regression tests cover cache hits, successful publication, cleanup after partial ContentTooShortError and URLError failures, and retrying after a failed download. The focused tests, the full tests/test_data suite, and pre-commit checks pass; repository-wide pytest runs were interrupted before completion with no failures observed before termination.

Any other comments?

None.

PR checklist

• The PR title starts with either [ENH], [MNT], [DOC], or [BUG]. [BUG] - bugfix, [MNT] - CI, test framework, [ENH] - adding or improving code, [DOC] - writing or improving documentation or docstrings.
• Added/modified tests
• Used pre-commit hooks when committing to ensure that code is compliant with hooks. Install hooks with pre-commit install.
  To run hooks independent of commit, execute pre-commit run --all-files

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
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Additional details and impacted files

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##             main    #2405   +/-   ##
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  Coverage        ?   88.20%           
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  Files           ?      200           
  Lines           ?    11174           
  Branches        ?        0           
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  Hits            ?     9856           
  Misses          ?     1318           
  Partials        ?        0           

Flag	Coverage Δ
cpu	88.20% <100.00%> (?)
pytest	88.20% <100.00%> (?)

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