Handle None and string values in Excel percent column

[jwalgran]

Overview

This change attempts to prevent exceptions when there are non-numeric values in an Excel column that mostly contains numbers formatted as percentages.

In addition we fix the handling of empty cells so that a None value is not
transformed into the string "None".

Connects https://github.com/open-apparel-registry/open-apparel-registry-clients/issues/85

Testing Instructions

• Check out develop
• Run ./scripts/resetdb
• Log in as c2@example.com and attempt to submit. percent-test-with-empty-and-string.xlsx
  Verify that an exception is raised
• Check out this branch bugfix/jcw/handle-none-and-string-in-percent-col
• Try submitting the workbook again and verify that it succeeds
• Use ./tools/batch_process {id} to process the list. Verify that there are 2 expected parse failures.
• Browse http://localhost:6543/settings select Embed and enable the percent_female_workers field and set the embed size
• Use the embed test at https://open-apparel-registry.github.io/embeded-map-test-full-width.html?host=localhost:6543&protocol=http&contributors=1 and verify that the facilities have correct values
  • KH EXPORTS has a product type but non of the other examples here has a product type of "None"
  • KH EXPORTS INDIA PRIVATE LTD shows 60% for percent_female_workers
  • SAGE CREATIONS shows fifteen percent for percent_female_workers
  • GAURAV does not have percent_female_workers value
  • CENTURY OVERSEAS has a parse error due to missing address
  • JIVA DESIGNS does not have a number of workers value but does have 18% for percent_female_workers

Checklist

• fixup! commits have been squashed
• CI passes after rebase
• CHANGELOG.md updated with summary of features or fixes, following Keep a Changelog guidelines

[emilyhu0106]

All the tests pass well! I also tried a few other wrong formats and they all work as expected. Nice work!

[emilyhu0106]

Good call for considering string here

[jwalgran]

Thanks for the review.