When the DevExpress upgrade wizard complains that it cannot change a file due to its encoding...

...you should:

1. shut Visual Studio 2013
2. revert the mess you just made (I hope you had your solution in source control.)
3. reopen the solution in Visual Studio 2013
4. say "No" when flagged to make a upgrade
5. find the objectionable files (I guess I should have mentioned that you should have made a list of these. Hopefully, you're not reading these instructions as you go.)
6. pick: Save YourFileNameHere.cs As... from the "File" menu for each messed up file and pick that little down arrow by the Save button to pick the "Save with Encoding..." option and when saving set the "Encoding:"
7. dropdown to "Unicode (UTF-8 with signature) – Codepage 65001"
8. close and reopen Visual Studio 2013
9. say "Yes"