Fix backward slash issue in user .csv lookup

[weilixu]

Pull request overview

A bug that makes Windows file path format not be able importing user data.

• Fixes #ISSUENUMBERHERE (IF THIS IS A DEFECT)

Pull Request Author

• Method changes or additions
• Data changes or additions
• Added tests for added methods
• If methods have been deprecated, update rest of code to use the new methods
• Documented new methods using yard syntax
• Resolved yard documentation errors for new code (ran bundle exec rake doc)
• Resolved rubocop syntax errors for new code (ran bundle exec rake rubocop)
• All new and existing tests passes
• If the code adds new require statements, ensure these are in core ruby or add to the gemspec

Review Checklist

This will not be exhaustively relevant to every PR.

• Perform a code review on GitHub
• All related changes have been implemented: method additions, changes, tests
• Check rubocop errors
• Check yard doc errors
• If fixing a defect, verify by running develop branch and reproducing defect, then running PR and reproducing fix
• If a new feature, test the new feature and try creative ways to break it
• CI status: all green or justified