Fix RBI workbook preprocessing

[rohitkumarbhagat]

No description provided.

[gemini-code-assist]

Code Review

This pull request refactors the preprocess_files function in rbi_download.py to write processed Excel sheets to a temporary directory before replacing the original file, ensuring atomic writes and preventing file corruption on failure. It also introduces a unit test in rbi_download_test.py to verify this behavior. The review feedback suggests moving the safe_to_numeric helper function outside of the loop to avoid redefinition, replacing the deprecated applymap method with map for pandas compatibility, and avoiding asserting on exact log messages in the unit test to prevent brittleness.

[gemini-code-assist]

Avoid writing tests that assert on exact log messages, as they are brittle and prone to breaking when log formats or wording change. Instead, assert that the logging function was called.

            fatal.assert_called_once()

References

1. Avoid writing tests that assert on log messages, as they are brittle.