I've just installed iOS 10.3 on an iPad Mini 4 (64bits) and my folders with names containing accents (ex: /Mes données/) are "not found" (no such file or directory)
Not vital as I can rename these folders and files, but strange, isn't it?
APFS...
This is because of what ever apple changed in the new Disk Format that 10.3 has.
If you don't have too many file/folder names with accents, it might be enough if you rename each of them, and delete and retype all the accented letters in the name. I don't have iOS 10.3 yet (and I probably don't have any filenames with accents or umlauts in Pythonista), so I haven't tested this myself. I'm only guessing based on what I know about the new APFS file system that iOS 10.3 uses.
I had some folders and I did rename them manually, it's ok and I understand it comes from the new file system, but I think it's not acceptable to so come back in the past...