Stuck working in a customer environment without my personal laptop, or the ability to install a lot of software.
Hit this bug:
https://quickview.cloudapps.cisco.com/quickview/bug/CSCvd21759
Basically, CUCM doesn’t like BOM headers in text files. Vanilla Notepad appears to add these by default. If you’re lucky enough to have a Linux box, this is an easy fix:
https://unix.stackexchange.com/questions/381230/how-can-i-remove-the-bom-from-a-utf-8-file
On windows, I used Notepad++ to re-encode the files to UTF-8:
https://stackoverflow.com/questions/32986445/remove-a-bom-character-in-a-file
UPDATE:
I found that this is in fact documented since 10.5.
Release Notes for Cisco Unified Communications Manager and IM and Presence Service, Release 10.5(1)
Incorrect Text Editor for Creating Text-Based CSV File
This documentation update resolves CSCvd21759.
The “Text-Based CSV Files” chapter in the Cisco Unified Communications Manager Bulk Administration Guide incorrectly state, you can create a CSV data file by using a text editor, such as Microsoft Notepad. The correct text editor to create a CSV data file is Notepad ++.
Using a text editor, such as Notepad++, you can select encoding as UTF-8 without Byte Order Mark (BOM) from the Encoding drop-down.
afterthenumber 
Thanks for sharing bro!
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