Ah, okay. I think I understand what happened here: When the patches were backed out the first time, for some reason the ICU data file was replaced with an empty file: <https://phabricator.services.mozilla.com/D116968?vs=450584&id=450646#change-c3mtSev48Kjf>. And when attempting to re-push the changes, the empty data file led the errors which caused the second backout.
Bug 1714933 Comment 14 Edit History
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Ah, okay. I think I understand what happened here: When the patches were backed out the first time, for some reason the ICU data file was replaced with an empty file: <https://phabricator.services.mozilla.com/D116968?vs=450584&id=450646#change-c3mtSev48Kjf>. And when attempting to re-push the changes, the empty data file led to the errors which caused the second backout.