I have created a “wic” directory in my custom layer and copied sdimage-bootpart.wks into it as sdimage-project.wks without making any changes but “wic list image” throws an error with the new .wks file:
UnicodeDecodeError: 'utf-8' codec can't decode byte 0xb0 in position 37: invalid start byte
Ignore that, I deleted the directory and tried again and it is OK now!
